If you like an RPG, Diablo style, there is also FLARE (Free/Libre Action Roleplaying Engine)

Lichess.org for online chess, or (most private of all) a physical travel board if you’re with a friend who wants to play. Lichess isn’t very private but definition though. Not sure why you asked in c/privacy? Anyway what happened to reading a book on a bus trip?

Oh try universal paperclips if you haven’t. 5 hours is about right for finishing it. That’s pretty private.

Anuto TD and Breakout 71 are good time killers on the phone. Open TTD if you are into sims and Cataclysm: Dark Days Ahead if you want post apocolyptic turn based survival horror rougelike. There are also quite a few RPG fangames based on Lisa the Painful.

Balatro

Battle for Wesnoth, if you’re into that kind of thing.

I usually turn to shattered pixel dungeon