On my Android tablet, my most used app has got to be either Mull (web browser, based on Firefox), NewPipe (YouTube client), or Tusky (Mastodon client).
My favourite app, however, is probably UntrackMe.
AdAway for Android via fDroid
Android
They're both pretty basic but honestly upon switching I realized how many superfluous features I didn't use in my old apps.
Simple Gallery (and the Simple Mobile apps in general), AdAway, SDMaid, Magisk, Firefox.
Nextcloud Notes for notes
Revanced for YouTube, Audacity, KDENlive, VLC, OBS studio, and the *ARR suite of applications.
Edit: I did not see that you said Android. Revanced it is then.
Revanced isn't open source. the patches are, but the base client is closed.
If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
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