@MrT10001, my deep respect! It worked!

Thank you so much!

@MrT10001 Let me try!
Can I just use CLI?

adb reboot bootloader
fastboot --slot=other flash bootloader **correct-mmage.img**
fastboot set_active other
fastboot reboot bootloader
fastboot set_active other
fastboot reboot bootloader
fastboot reboot

P.S. I installed the deb package and ran it from the menu (not from a terminal), the result was the same.

P.P.S After installation the phone in UBports Recovery with options reboot, Advance, and Factory reset. lsusb sees the device

Bus 003 Device 016: ID 18d1:d001 Google Inc. Nexus 4 (fastboot)

However, if I press reboot, it stuck in the fastboot screen and doesn't move in any way.

@MrT10001
OOPS! Sorry, I missed the link to the video.
Here is the recording

Note: I skipped the drivers and rules installation because they were installed at first launch of the installer

@MrT10001 Thank you for looking in my problem!

• ROM: Hm, I don't know! The installer (1) detected the device correctly, (2) instructed me how to get to the developer mode on android, enable OEM, enable USB debugging, (3) instructed me how to disable boot lock, (4) did it magic. How can I check that the installer installed the correct ROM?
• ADB and Fastboot drivers: the same. How can I check that they are the latest?
• The installer picks the device and said that it flash boot, then installer reboots the device and asks to turn into rescue mode and says it installing the main OS (see video)
• I'm running it from a terminal, but without sudo. At first run, the installer asked for the root privileges to install drivers and correct udev rules - i allowed.
• as you can see from the video, I'm installing 20.04 (stable)

@MrT10001 said in Failed to install os on Google Pixel 3a:

I have put the correct ROM on using the Android Recovery Tool with Chrome Browser - IT HAS to be Chrome, it won't work on other browsers. This has always worked for me on the Pixel Phones. Fastboot should work, but doesn't always when getting to the correct ROM. When the correct ROM is installed, set up Android first before attempting a UT install.

Sorry I don't get that. Where did you put it and how to install the correct ROM?

Thank you again

Completely new to Ubuntu Touch and Android, but I have more than 20 years of experience as a Linux user/developer/sysadmin (once I built the LFS :P)

A completely new Google Pixel 3a was bought to install Ubuntu Touch. I download a fresh installer (app image, ubports-installer_0.10.0_linux_x86_64.AppImage) from the official website. My main computer runs PoP_OS! I diligently followed instructions but ended up in recovery mode. Several attempts to reinstall OS did not work. I screen-recorded the last attempt.

I might do something silly, but I can't find a way out. I stuck into fastboot mode or, just after installation, in recovery mode (see video).

What did I do wrong?