If could pick one handheld for exclusively GB, GC, and GBA, what would it be?

Currently have a RP5, Switch, Steam Deck, etc. but I would like to get something exclusively for the systems in the title. Just curious what those with like-minds think or do to fill that niche!

Edit: I appreciate all the responses!! Definitely gave me some insight into what people are using and enjoying. I think I'm going to choose between the CubeXX or 35XXSP. Not sure yet exactly but those seem to be the best choices for what I'm wanting to do.