In my experience of maintaining Arch, it’s as simple as:
-Keep your packages up to date -Keep your mirrorlist up to date -install a package called “pacdiff” and run it after every update (certain config files need to be manually replaced/updated after system updates, pacdiff handles this for you. This actually includes your mirrorlist).
Anything else really just boils down to individual issues with packages which could happen on any distro, or really and OS in general. As another user said, if you got Arch installed as a newer Linux user, you’re already doing well.
F droid is totally usable. Simply download and install the APK from their website and allow installation from unknown sources when prompted.
Unfortunately, e/OS or other Android roms are off the table as the bootloaders are locked (at least in my country they are, someone can correct me if that’s not the case worldwide).