Mobilism - https://forum.mobilism.org/viewforum.php?f=398
Mods.

4PDA - https://4pda.to/forum/index.php?showforum=212

F-Droid - https://f-droid.org/

APKMirror - https://www.apkmirror.com/

Apps

foobar2000 - https://www.foobar2000.org/android
Music player.

eBoox - Google Play
Reader for EPUBs.

Pocketbook - Google Play
Reader for PDFs and DJVUs.

Home Dictionary - https://github.com/mortalis13/HomeDictionary/releases
Great app for .dsl dictionaries.

Feeder - Google Play
Open source RSS reader.
Feeds: essentials.opml

Smart AudioBook Player - Mobilism
Good audiobook player.

AntenaPod - Google Play
Open source podcast app.

LibreTorrent - https://github.com/proninyaroslav/libretorrent/releases
Open source Bittorent client.

Firefox - Google Play
Don’t use Google Chrome. Google went full totalitarianism removing uBlock. Firefox Android app can install same extensions as desktop browser. Firefox is the GOAT.

Youtube Revanced

1) Revanced Manager - https://revancedmanager.com/

2) Youtube APK - https://www.apkmirror.com/uploads/?appcategory=youtube