Yes, now the google flash tool works correctly!

@MrT10001 I installed Android again with google flash tool and now it works! (Perhaps because now ADB is installed on my PC)
Thank you very much for your help!!!
Tomorrow I try to install ubuntu touch again, hopefully without any problem
Have a nice evening,
Best wishes
Stefan

@arubislander Thank you for your quick answer - so I leave everything how it is. It is just a blemish.
Have a nice weekend

Good day!
After some trouble I finally installed ubuntu touch on my Pixel 3a XL successful.
When I start the phone I see the two screens

before ubuntu touch starts.

Is it possible to undo unlocking the phone?

Thank you in advance
Stefan

@MrT10001 I installed Android again with google flash tool and now it works! (Perhaps because now ADB is installed on my PC)
Thank you very much for your help!!!
Tomorrow I try to install ubuntu touch again, hopefully without any problem
Have a nice evening,
Best wishes
Stefan

@MrT10001 I changed the slot and now the phone boots to recovery mode!

I have the following andvanced options:

What shall I do now? (I ask because the last time I tried something in the advanced options I could never enter again to this mode)

@MrT10001 After solving the problem to find the path for fastboot (/usr/lib/android-sdk/platform-tools) it worked like you described. But the slot B was already active.

Additional information: At this search I found out, that ADB was not installed and so I installed it.

Thanks a lot
Stefan

@MrT10001 Sorry, what means fastboot terminal?

@stanwood

When I start the smartphone after installing Android 9 with Flashtool in Chrome, I see the screen of the first picture of this thread and than the white google-screen which stays and crashes.

How I said I need Android 9 to install ubuntu touch on the smartphone.

Did I use a wrong build which does not work on this phone or do I have to do something before starting Android 9 on the smartphone?

Yes, now the google flash tool works correctly!

@MrT10001 This was a good hint! After entering the command 'fastboot devices' ubuntu informed me that fastboot is not installed. After installing fastboot the command 'sudo ./flash-all.sh' worked.
Unfortunately after installing the android system does not start. The white google-screen stays.

Here is the content of the terminal:

sm@sm-ESPRIMO-P900:~/Schreibtisch/Pixel 3a XL/PQ3B.190801.002/bonito-pq3b.190801.002$ fastboot devices
Der Befehl 'fastboot' wurde nicht gefunden, kann aber installiert werden mit:
sudo apt install fastboot                                 # version 1:33.0.3-2, or
sudo apt install google-android-platform-tools-installer  # version 34.0.4+1695033340
sm@sm-ESPRIMO-P900:~/Schreibtisch/Pixel 3a XL/PQ3B.190801.002/bonito-pq3b.190801.002$ sudo apt install fastboot
[sudo] Passwort für sm:       
Paketlisten werden gelesen… Fertig
Abhängigkeitsbaum wird aufgebaut… Fertig
Statusinformationen werden eingelesen… Fertig
Die folgenden Pakete wurden automatisch installiert und werden nicht mehr benötigt:
  linux-headers-6.8.0-40 linux-headers-6.8.0-40-generic linux-headers-6.8.0-41
  linux-headers-6.8.0-41-generic linux-headers-6.8.0-44
  linux-headers-6.8.0-44-generic linux-headers-6.8.0-45
  linux-headers-6.8.0-45-generic linux-image-6.8.0-40-generic
  linux-image-6.8.0-41-generic linux-image-6.8.0-44-generic
  linux-image-6.8.0-45-generic linux-modules-6.8.0-40-generic
  linux-modules-6.8.0-41-generic linux-modules-6.8.0-44-generic
  linux-modules-6.8.0-45-generic linux-modules-extra-6.8.0-40-generic
  linux-modules-extra-6.8.0-41-generic linux-modules-extra-6.8.0-44-generic
  linux-modules-extra-6.8.0-45-generic linux-tools-6.8.0-40
  linux-tools-6.8.0-40-generic linux-tools-6.8.0-41
  linux-tools-6.8.0-41-generic linux-tools-6.8.0-44
  linux-tools-6.8.0-44-generic linux-tools-6.8.0-45
  linux-tools-6.8.0-45-generic
Verwenden Sie »sudo apt autoremove«, um sie zu entfernen.
Die folgenden zusätzlichen Pakete werden installiert:
  android-libbase android-libboringssl android-libcutils android-liblog
  android-libsparse android-libziparchive android-sdk-platform-tools-common
Vorgeschlagene Pakete:
  android-sdk-platform-tools
Die folgenden NEUEN Pakete werden installiert:
  android-libbase android-libboringssl android-libcutils android-liblog
  android-libsparse android-libziparchive android-sdk-platform-tools-common
  fastboot
0 aktualisiert, 8 neu installiert, 0 zu entfernen und 0 nicht aktualisiert.
Es müssen 1.173 kB an Archiven heruntergeladen werden.
Nach dieser Operation werden 3.561 kB Plattenplatz zusätzlich benutzt.
Möchten Sie fortfahren? [J/n] J
Holen:1 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-liblog amd64 1:34.0.4-1build3 [35,8 kB]
Holen:2 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-libbase amd64 1:34.0.4-1build3 [99,0 kB]
Holen:3 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-libboringssl amd64 14.0.0+r11-4build1 [729 kB]
Holen:4 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-libsparse amd64 1:34.0.4-1build3 [25,8 kB]
Holen:5 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-libziparchive amd64 1:34.0.4-1build3 [40,7 kB]
Holen:6 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-sdk-platform-tools-common all 28.0.2+9 [6.402 B]
Holen:7 http://archive.ubuntu.com/ubuntu noble/universe amd64 android-libcutils amd64 1:34.0.4-1build3 [35,7 kB]
Holen:8 http://archive.ubuntu.com/ubuntu noble/universe amd64 fastboot amd64 1:34.0.4-1build3 [201 kB]
Es wurden 1.173 kB in 0 s geholt (2.525 kB/s).
Vormals nicht ausgewähltes Paket android-liblog:amd64 wird gewählt.
(Lese Datenbank ... 695516 Dateien und Verzeichnisse sind derzeit installiert.)
Vorbereitung zum Entpacken von .../0-android-liblog_1%3a34.0.4-1build3_amd64.deb
 ...
Entpacken von android-liblog:amd64 (1:34.0.4-1build3) ...
Vormals nicht ausgewähltes Paket android-libbase:amd64 wird gewählt.
Vorbereitung zum Entpacken von .../1-android-libbase_1%3a34.0.4-1build3_amd64.de
b ...
Entpacken von android-libbase:amd64 (1:34.0.4-1build3) ...
Vormals nicht ausgewähltes Paket android-libboringssl:amd64 wird gewählt.
Vorbereitung zum Entpacken von .../2-android-libboringssl_14.0.0+r11-4build1_amd
64.deb ...
Entpacken von android-libboringssl:amd64 (14.0.0+r11-4build1) ...
Vormals nicht ausgewähltes Paket android-libsparse:amd64 wird gewählt.
Vorbereitung zum Entpacken von .../3-android-libsparse_1%3a34.0.4-1build3_amd64.
deb ...
Entpacken von android-libsparse:amd64 (1:34.0.4-1build3) ...
Vormals nicht ausgewähltes Paket android-libziparchive:amd64 wird gewählt.
Vorbereitung zum Entpacken von .../4-android-libziparchive_1%3a34.0.4-1build3_am
d64.deb ...
Entpacken von android-libziparchive:amd64 (1:34.0.4-1build3) ...
Vormals nicht ausgewähltes Paket android-sdk-platform-tools-common wird gewählt.
Vorbereitung zum Entpacken von .../5-android-sdk-platform-tools-common_28.0.2+9_
all.deb ...
Entpacken von android-sdk-platform-tools-common (28.0.2+9) ...
Vormals nicht ausgewähltes Paket android-libcutils:amd64 wird gewählt.
Vorbereitung zum Entpacken von .../6-android-libcutils_1%3a34.0.4-1build3_amd64.
deb ...
Entpacken von android-libcutils:amd64 (1:34.0.4-1build3) ...
Vormals nicht ausgewähltes Paket fastboot wird gewählt.
Vorbereitung zum Entpacken von .../7-fastboot_1%3a34.0.4-1build3_amd64.deb ...
Entpacken von fastboot (1:34.0.4-1build3) ...
android-sdk-platform-tools-common (28.0.2+9) wird eingerichtet ...
android-liblog:amd64 (1:34.0.4-1build3) wird eingerichtet ...
android-libboringssl:amd64 (14.0.0+r11-4build1) wird eingerichtet ...
android-libbase:amd64 (1:34.0.4-1build3) wird eingerichtet ...
android-libziparchive:amd64 (1:34.0.4-1build3) wird eingerichtet ...
android-libcutils:amd64 (1:34.0.4-1build3) wird eingerichtet ...
android-libsparse:amd64 (1:34.0.4-1build3) wird eingerichtet ...
fastboot (1:34.0.4-1build3) wird eingerichtet ...
Trigger für libc-bin (2.39-0ubuntu8.3) werden verarbeitet ...
Trigger für man-db (2.12.0-4build2) werden verarbeitet ...
sm@sm-ESPRIMO-P900:~/Schreibtisch/Pixel 3a XL/PQ3B.190801.002/bonito-pq3b.190801.002$ fastboot devices
no permissions (missing udev rules? user is in the plugdev group); see [http://developer.android.com/tools/device.html]	 fastboot

sm@sm-ESPRIMO-P900:~/Schreibtisch/Pixel 3a XL/PQ3B.190801.002/bonito-pq3b.190801.002$ sudo ./flash-all.sh
Warning: skip copying bootloader_b image avb footer (bootloader_b partition size: 0, bootloader_b image size: 8550056).
Sending 'bootloader_b' (8349 KB)                   OKAY [  1.250s]
Writing 'bootloader_b'                             (bootloader) Flashing Pack version b4s4-0.1-5653622
(bootloader) Flashing partition table for Lun = 0
(bootloader) Flashing partition xbl_b
(bootloader) Flashing partition xbl_config_b
(bootloader) Flashing partition tz_b
(bootloader) Flashing partition aop_b
(bootloader) Flashing partition hyp_b
(bootloader) Flashing partition keymaster_b
(bootloader) Flashing partition cmnlib_b
(bootloader) Flashing partition cmnlib64_b
(bootloader) Flashing partition abl_b
(bootloader) Flashing partition devcfg_b
(bootloader) Flashing partition qupfw_b
(bootloader) Flashing partition storsec_b
OKAY [  0.307s]
Finished. Total time: 1.996s
Rebooting into bootloader                          OKAY [  0.048s]
Finished. Total time: 0.099s
< waiting for any device >
Warning: skip copying radio_b image avb footer (radio_b partition size: 0, radio_b image size: 74739852).
Sending 'radio_b' (72988 KB)                       OKAY [  8.570s]
Writing 'radio_b'                                  (bootloader) Flashing Pack version SSD:g670-00011-190411-B-5457439
(bootloader) Flashing partition modem_b
OKAY [  0.474s]
Finished. Total time: 9.449s
Rebooting into bootloader                          OKAY [  0.019s]
Finished. Total time: 0.069s
--------------------------------------------
Bootloader Version...: b4s4-0.1-5653622
Baseband Version.....: g670-00011-190411-B-5457439
Serial Number........: 9ANAX0LTUF
--------------------------------------------
extracting android-info.txt (0 MB) to RAM...
Checking 'product'                                 OKAY [  0.059s]
Checking 'version-bootloader'                      OKAY [  0.059s]
Checking 'version-baseband'                        OKAY [  0.060s]
Setting current slot to 'b'                        OKAY [  0.067s]
extracting boot.img (64 MB) to disk... took 1.903s
archive does not contain 'init_boot.img'
extracting dtbo.img (8 MB) to disk... took 0.042s
archive does not contain 'dt.img'
archive does not contain 'pvmfw.img'
archive does not contain 'recovery.img'
extracting vbmeta.img (0 MB) to disk... took 0.000s
archive does not contain 'vbmeta_system.img'
archive does not contain 'vbmeta_vendor.img'
archive does not contain 'vendor_boot.img'
archive does not contain 'vendor_kernel_boot.img'
archive does not contain 'super_empty.img'
archive does not contain 'boot_other.img'
archive does not contain 'odm.img'
archive does not contain 'odm_dlkm.img'
archive does not contain 'product.img'
extracting system.img (2278 MB) to disk... took 86.592s
archive does not contain 'system_dlkm.img'
archive does not contain 'system_ext.img'
extracting system_other.img (392 MB) to disk... took 14.777s
extracting vendor.img (523 MB) to disk... took 19.338s
archive does not contain 'vendor_dlkm.img'
archive does not contain 'vendor_other.img'
extracting boot.img (64 MB) to disk... took 0.658s
archive does not contain 'boot.sig'
Sending 'boot_b' (65536 KB)                        OKAY [  2.020s]
Writing 'boot_b'                                   OKAY [  0.659s]
extracting dtbo.img (8 MB) to disk... took 0.080s
archive does not contain 'dtbo.sig'
Sending 'dtbo_b' (8220 KB)                         OKAY [  0.316s]
Writing 'dtbo_b'                                   OKAY [  0.406s]
extracting vbmeta.img (0 MB) to disk... took 0.000s
archive does not contain 'vbmeta.sig'
Sending 'vbmeta_b' (4 KB)                          OKAY [  0.122s]
Writing 'vbmeta_b'                                 OKAY [  0.066s]
archive does not contain 'super_empty.img'
extracting system.img (2278 MB) to disk... took 68.717s
archive does not contain 'system.sig'
Sending sparse 'system_b' 1/9 (262140 KB)          OKAY [ 22.868s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 2/9 (262140 KB)          OKAY [ 37.686s]
Writing 'system_b'                                 OKAY [  0.386s]
Sending sparse 'system_b' 3/9 (262140 KB)          OKAY [ 17.633s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 4/9 (262140 KB)          OKAY [  8.336s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 5/9 (262140 KB)          OKAY [ 13.696s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 6/9 (262140 KB)          OKAY [ 10.936s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 7/9 (262140 KB)          OKAY [  9.036s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 8/9 (258620 KB)          OKAY [  8.496s]
Writing 'system_b'                                 OKAY [  0.373s]
Sending sparse 'system_b' 9/9 (239920 KB)          OKAY [ 12.786s]
Writing 'system_b'                                 OKAY [  1.570s]
extracting system_other.img (392 MB) to disk... took 7.005s
archive does not contain 'system_other.sig'
Sending sparse 'system_a' 1/2 (262140 KB)          OKAY [  7.769s]
Writing 'system_a'                                 OKAY [  0.373s]
Sending sparse 'system_a' 2/2 (140000 KB)          OKAY [  4.236s]
Writing 'system_a'                                 OKAY [  1.090s]
extracting vendor.img (523 MB) to disk... took 4.632s
archive does not contain 'vendor.sig'
Sending sparse 'vendor_b' 1/3 (262140 KB)          OKAY [  7.929s]
Writing 'vendor_b'                                 OKAY [  0.373s]
Sending sparse 'vendor_b' 2/3 (261472 KB)          OKAY [  7.876s]
Writing 'vendor_b'                                 OKAY [  0.373s]
Sending sparse 'vendor_b' 3/3 (12276 KB)           OKAY [  1.286s]
Writing 'vendor_b'                                 OKAY [  0.470s]
Rebooting                                          OKAY [  0.011s]
sm@sm-ESPRIMO-P900:~/Schreibtisch/Pixel 3a XL/PQ3B.190801.002/bonito-pq3b.190801.002$

@MrT10001 Ok. I ran flash-all.sh with 'sudo ./flash-all.sh'
Alter entering the pasword the cursor is flashing. Is it possible that I have to wait for a long time?