Well, there are a few ISAs (Instruction Set Architectures) supported by Android. They are armv8 (aarch64 or arm64), armv7 (armhf), and x86_64 (amd64). Every SoC does not have a completely different instruction set. Whatever you read has no idea what they're talking about I guess, or you did not understand it properly. We also do not use VMs or ART for the Android portions we need.

@sam-strelitz Just a note. Graphene OS website gives an excelent command line tutorial,Linux, Mac, or Windows, for flashing the Pixel 3a. Worked flawlessly for me.

@sam-strelitz Getting some piece of FOSS software compiled and starting on a phone is trivial. Making it useful on a phone is not. The difference is phones have limited battery and limited connectivity, and aren't designed to be in active use 24/7. And traditional apps made for traditional PCs don't tend to take such things into consideration, or are they designed to work with touch input or scale properly on a small screen that is 300-600 DPI. I can see that you are quite excited, but if you are expecting your phone experience to be like you are used to having on a PC, you are going to be woefully disappointed (either because that isn't what you get, or because when you do get that it will be a horrible experience).