Updated to LineageOS 23.0, removed GAPPS, cannot install F-Droid?

Got a free evening and decided to upgrade SAMSUNG Galaxy Tab A7 10.4 (SM-T500) (gta4lwifi) to a new version of android.
- all good, restart tablet, go through setup, everything works, download f-droid apk, grant permission for installing from another source, press install

LOS says:

"App not installed."

That's it, no error, no nothing. Did I mess up the upgrade? Reading up on the issue online and maybe f-droid has not yet been updated to android 16? How do I go about figuring out what the issue is?