Legends of runeterra has a single player campaign that is probably the funnest card game ive ever played. There are in app purchases, but ive been playing off and on for about 6 years and ive never bought anything. No ads either. Rogue card adventure i think is another really good one despite the less than impressive name.

Optionally, its fully possible to get an emulator on your phone. Id recommend a bluetooth controller (a lot of older phones wont allow wired controllers even with the adapter, but ime every phone allows bluetooth controllers) but its not required. You can emulate any game from atari all the way up to gamecube on the shittiest $20 walmart phone with a screen.

Finally, as long as you are on android, technically you can get almost any app for free. Super illegal and they definitely (wont) prosecute you, so i would highly advise against checking websites like apkaward, as you might find malicious programs that install fully playable games on your device, such as the amazing star wars:knights of the old republic 2 android port that can be found on that site. Fair warning though, if you accidently end up up with kotor 2 on your phone id highly recommend getting the content restored mod. It adds back in all the cut content and fixes a slee of potentially gamebreaking bugs. On current android you do have to use a conputer to install the mod, but its very easy and i can help you with that part as it is entirely legal.