My View on installing on Mi A2
Got hold of a Mi A2 today, so ubuntu touch must go on it, so here are my observations for the install.
Two computers ready, one with windows 10, USB 3.1, the other with Ubuntu 21.04, USB2 and 3.
The phone was on Android 10, set OEM unlock and USB debugging, booted to bootloader and did :
./fastboot oem unlock
(windows 10 Powershell), all going good so far. Ran the installer and it failed.
Switched to the Ubuntu machine, and couldn't get the vendors image file to transfer. Put it in the root of the home folder and it just would not go. So couldn't go any further there, so back to windows 10.
So back on windows, I could not get it to pushing files to the device, it failed every time with an ADB issue and wouldn't write to the partitions.
Dropped back to Android 9 and had the same issues. I then tried:
./fastboot oem lock ./fastboot oem unlock_critical
This locked the bootloader again then the critical unlock unlocked "critical" partitions so they could be written too.
Still failed with an ADB issue, so I updated my Android Studio and voila, installed like a charm.
So another phone to test - only thing so far is the front camera switches on the light (sore eyes).
So again, moral is to persevere, persevere and persevere. Installing boot files and halium-9 recovery takes about 5 minutes and there appears to be nothing going on. Leave things alone, till the installer tells yo to go to the next step. After that it goes pretty quickly compared to some other devices.
I would like to finish off by thanking the developers, these forums and XDA-forums who give some great advice and ideas. Keep up the good work.