Are there any FOSS Mahjong apps for an elderly person?
My grandmother wants to install Mahjong onto her phone. I couldn't find any results on the Play Store with no ads or in-app purchases. She doesn't understand technology and could get tricked into purchasing stuff or compromising her data.
Do you know what she actually wants to play? Mahjong is a multiplayer game, usually played with four players. Shisen-Sho is a singleplayer game but it is colloquially called Mahjong. When someone says Mahjong they often mean Shisen-Sho without even realising there is a difference.
It's unlikely but if she wants Japanese riichi mahjong and not solitaire style, Kemono Mahjong is a really solid app. No ads or micro transactions (the only in app purchase is to optionally support the dev for $1/month), full feature, minimal to no tracking (email address for online game purposes). It's not open source or free but it's only $3 one time purchase.
I don't have any suggestions for solitaire/tile matching mahjong, unfortunately. Microsoft's app is not malware but will be datamine galore. It also has ads unless you pay per month. Anything else, id be leery of the security of the app and your data.