I think often you don't get the sale for most phones as android is not often installable on many old phones. So getting linux or other stuff to install and use is the only option.
Not sure if I posted about this RPG but it has pretty good narrative and something worth playing if you are into JRPGs.
The graphics is pretty good for the RPG and on mobile it's fun to play.
One of the Kemco's game "Bonds of the Skies" is on android, I thought I should share here. It's paid game but if you are into their game then yes you won't be disappointed.
All of them are free and you can get them by searching google. Which tool to use for which game is totally your choice. Again all of them are free but you have to spend money on raspberry pi hardware and the displays and controllers. Making small size console to big arcade cabinet would take time and money too.