Supposing there are some, that is? It seems like an underappreciated side of custom firmware & homebrew that it may enable the creation of altogether new games, if the scene has developed enough.
Also if there may be a better community to ask this, let me know!
I don’t think this is the best game ever, but I used to have (and still have actually) this homebrew game called World of Sand, in my R4, I found it quite simple and relaxing.
A sandbox game, literally.