Mobile games usually get a bad rep as they’re usually asset flips and/or MTX-ridden and/or ad-filled, etc., and I’m sure this is actually the case for most games on the app/play store. But are there any ones that are actually good, maybe just something to pass the time with?
Look for old games, that were released a long time ago before the “predation” was so required.
Osmos and World of Goo come to mind. Monument Valley 1 was a more popular, recent one in that vein.
Other than that, the FOSS and emulation recommendations here are great.