AFAIK you can still install any random APK but the process will require enabling developer mode and one time 24 hour wait period. But the problem is many stupid Apps check that developer mode is on and refuse to work.
An FDroid desktop client that adb installs APKs would actually be lovely. I pretty much exclusively use FDroid, but I gotta say I unfortunately find all their frontends to be rather buggy and with very little user feedback when things break (repo updates are hard to observe, downloads hang, updates mysteriously fail)
How long before they take that option away?
I'm not aware of any apps that check for developer mode, that's mainly root.
> many stupid Apps check that developer mode is on and refuse to work
Do you have some examples? I have developer mode enabled and have never seen any apps complaining (and I have used a lot of different banking apps).