A few I haven't seen mentioned:
- Moon+ Reader - My favorite ebook reader of all time.
- Tea Time - Simple timer widgets
- Simple Time Tracker - Track what you do
- NES.emu, Snes9x EX+, M64+ FZ - Emulators
- Thunder - Lemmy
- Root Explorer - file explorer
- Lichess - Chess, free of ads, no fees. Almost entirely FOSS.
Also +1 to the usual favorites: Firefox, Termux, Nova, etc.
Unfortunately, no, you just need training data on children in general and training data with legal porn, and these tools can combine it.
It's already being done, which is disgusting but not surprising.
People have worried about this for a long time. I remember a subplot of a sci-fi series that got into this. (I think it was The Lost Fleet, 15 years ago).