@MrT10001 said in Possible to install UT 20 over UT 16 on Google Pixel 3a XL using UBports Installer without first flashing Android back onto the phone?:

Yes, I would use the installer rather than the update channel and tick the "wipe data" option to start afresh. This will remove all your data so back up first. This will remove all apps as well so you won't have incompatible ones left.

Thanks! It appears that I may have achieved a similar result by first installing UT 20 over 16 via OTA, then resetting the device using Erase & Reset All. Certainly, all of my installed apps, all personal files and all configurations were wiped.

@MrT10001 said in Possible to install UT 20 over UT 16 on Google Pixel 3a XL using UBports Installer without first flashing Android back onto the phone?:

I would only ever reinstall Android back on my UT devices if they "soft bricked" and even then I have found it is not always necessary.

Yes, that seems to fit a scenario where either the "correct" version of Android or some functioning version of UT would be a prerequisite to install UT via Installer.