Anbernic RGP35XXSP on the left sporting MuOS. Fits just fine in my original GBA case!
On the right is my Miyoo Mini+ in a 3D printed hard case (from Etsy) running OnionOS.
The Anbernic is quickly becoming my go-to due to the RTC, which makes Pokemon games easier to enjoy. And being able to just flip the lid shut to sleep and power off after ten minutes is very nice. But I still vastly prefer the UI of OnionOS on the MM+.
All kinds of stuff! Most systems up to PS1 work just fine, but I stick to mostly stuff made for smaller screens. So other handhelds like GBA, GBC, Game Gear, WonderSwan, etc...
I have been rocking the Miyoo mini plus! Loving onion OS too! My main complaint is it's charging tho, I have USB C PD charges all over the house for everything else (phone, laptop Steamdeck, switch ect...) And it's so frustrating that the Miyoo does not work with that.