Infinity (Reddit client), Pdf Viewer Plus (PDF viewer), Book Reader (Epub files), Signal (communication), Briar (communication), File Manager, Gallery (picture viewer), Calendar, Syncthing (cloudless syncing of files between devices), Scrambled (get rid of meta-data on photos), Feeder (RSS feeder), and SkyTube/NewPipe Legacy (youtube), Music Player GO (music - local files :P), and Termux (terminal), fennec (Firefox-like web browser (I think Mozilla itself is behind this project? It's actually very slick)), Jitsi (video meetings).