UBports flashing failed half-way

[PhAndersson]

Hello,
I got a refurbished Pixel 3a delivered with Android 12 and was able to unlock its bootloader and downgrade it to Android 9 (PQ3B.190801.002) using the web-based Android Flash Tool.
I then attempted the UT installation using 'ubports-installer' version 0.9.7-beta (upon startup, it suggested that "snap refresh --stable", but snap told me that no update was available).
I selected channel "20.04/arm64/android9plus/stable" and the UT installation process started (it said "flashing firmware"), then asked me to reboot the phone in recovery, which I tried to do -- the phone seemed stuck on the white "Google" splash screen. 'ubports-installer' was never able to re-establish the communication with the device.
I tried power-cycling the phone, booting it to bootloader and switching to recovery mode again, but this no longer works -- it returns by itself to the bootloader with a message at the bottom saying "failed to boot boot.img" (or some such).
Any idea as to how I should proceed? (try to re-flash Android 9? retry immediately with UBP-installer?)
Also, is version 0.9.7-beta of UBP-installer the recommended one?
TIA
Ph. A.

[MrT10001]

@PhAndersson Flash back to Android 9 and make sure your phone works. Then use the latest version on the installer (0.10.0) which will be on edge to install UT.

[PhAndersson]

@MrT10001 Thanks -- I'll try that.

[PhAndersson]

For the benefit of the community: due to my failed flashing attempt, the phone was left in a state where only the bootloader could be reached. It displayed a message saying: "no valid slot to boot".

As suggested by @MrT10001, I was able to get it back to a functioning state by re-flashing it with Android 9 (PQ3B.190801.002) using the 'flash-all.sh' script.

I'll try again the UT installation using the UBP-installer v0.10.0 this time and report back on the outcome.

[stanwood]

@PhAndersson If the Snap package doesn't work well, you can get the latest UBports Installer AppImage version here: https://devices.ubuntu-touch.io/installer/ which works like a charm on my Xubuntu laptop.

If the device fails to reboot in recovery mode, you may try to force the behavior using: (in the terminal)

adb reboot recovery

Also, ensure you have ticked all the boxes "Wipe data" + "Bootstrap partition", etc...

[PhAndersson]

@stanwood Thanks a lot for the advice.

[PhAndersson]

I just installed the phone with UBP-installer v0.10.0 -- everything went like a charm this time round.

Many thanks to both of you for your support.

[Vlad Nirky]

@PhAndersson
Congrats and welcome!