I only know the way I linked to.
The App is not installed for you as a user, I guess you would have to live with that then.
The solution in this case is to build your own Android and remove the stuff you don’t like from the source code.
The “bare-bones Android” would be AOSP, on which every Android OS out there is based.
LineageOS is close to what AOSP would be like.
Yes. You don’t install hardware drivers as a user, they are built into Android, apart from basic stuff mostly by the smartphone vendors so Android works with their phone’s hardware.
If you would want to change something there, you would have to build your own Android.
He was talking about AOSP, which uses the proprietary drivers. The GSI idea (which indeed didn’t exist when FP1 came out) also relies on proprietary drivers. If you are looking for a real Linux distribution, you should support postmarketOS. However, there has not been any work implementing pmOS on FP3.