I really like Aegis for 2FA/TOTP:

https://github.com/beemdevelopment/Aegis

Edit: also Element, a matrix client, for messaging: https://element.io/download

Edit 3: Feeder for RSS (Google Play), (F-Droid), I really like how you can extract the text of articles without ads.

Edit 4: Simon Tatham’s Puzzles, a bunch of simple puzzle games, no ads or BS (Google Play) (I think this is the right one: F-Droid). Fun fact: he created PuTTY.

Edit 2: also minidlna (apparently called ReadyMedia now) as a UPnP/DLNA server to host music and videos on your PC, then you can easily watch using VLC on a phone/computer (and any smart TV with the VLC app, probably) within the LAN. I’d be interested to hear any recommendations for how to easily access my UPnP server from outside my network from my phone. I’m sure there’s some way to do it with a VPN, but I’d rather only route the media streaming traffic through my home network, not all my phone’s traffic.