Why do you keep harping on about ADB installs. That's not helpful. It doesn't help me install open source apps from FDroid. It's ridiculous that you think booting up a computer and using ADB is a reasonable workaround. It isn't.
You would be able to install f droid and it's apps without going through this flow.
If you enable the advanced flow as described in the Android Developers Blog, then you can install unregistered apps regardless of source. That includes apps from sources like F-Droid.