As in title, preferably open-source, but doesn’t have to, I will start:
KOReader - Amazing reader app, and being able to use the same app across various devices, even non-android ones, is pure bliss. Japanese support is pretty good too, which makes me happy. Though… Sadly no vertical text support :c
Syncthing-fork - Being able to keep a library of books, and some files, and easily keep the shared folder across various devices, is mega comfy. Tachiyomi - Cute manga reader.
NewPipe - Really pleasant youtube client, that i sometimes use to listen to things in the background.
Kaku - An useful Japanese OCR app, that works… quite decently for when I encounter kanji that I do not recognize, and is not text.
EinkBro - A web browser, that on e-ink devices, is quite comfy. Has few… quirks, but works well on e-ink
Is netguard still maintained? I seem to recall seeing the developer freeze development maybe a year or two ago? Hopefully I’m wrong.
Looks healthy. There was activity and new releases in 2021, 2022 and June 2023. Also, the app might be near feature complete, and if that’s the case there will only be sporadic work left like keeping it updated/compatible or fixing security ssues.