I want to add OpenTTD and Battle for Polytopia to the list.
OpenTTD is a free as free can be transport simulation. You have to get used to the controls, but I had some fun with it on my android tablet. Although I prefer to play it on PC.
Battle for Polytopia is a Civilization style game with awesome Voxel graphic for mobile devices. One game in standard mode lasts about an hour. It is free2play in a way that you get the game and the first 3 civilizations for free and can buy additional ones for a small fee. Offline playing is possible and I've never seen any ads in it.
Oh, and of course try Gwent.
This is a CCG in the world of The Witcher - known from the books, the games and of course the Netflix series too.
It's free to play, and very generous to free players. No ads, no pay2win, and you gain ressources to craft your cards very fast.
If you want to see some gameplay: I am streaming it every wednesday on Twitch.
If you want to avoid the hassle that it takes to set up a Microsoft account you may try Minetest instead of Minecraft.
It's an free and Open Source reimplementation that needs no Java, and the game mode "Mineclone" is very close to the original.
Regardings RTS I can recommend Supreme Commander: Forged Alliance
I you want to try out a business simulation you may look at OpenTTD which is free (and free of ads) over Steam.
Well,
especially if he has additional health issues he should go for his vaccine. Of course it's not a guarantee, but it lowers the risk for a serious illness significantly.
And it's still not an excuse to stay away from a courtroom.