MiyooCFW VS SimUI

Try getting a second SD card and flashing it with the Miyoo cfw from here. It's probably something corrupted on the card.

And/or just install one of the nightly builds yourself and see what issues you find. They can be found under the actions tab on github, although I think you have to be logged in to actually see the download: https://github.com/TriForceX/MiyooCFW/actions/workflows/build.yml

Generally speaking RetroArch allows installing and removing cores, but no clue how it works on this device and what the steps are if its possible. This article or tutorial might interest you: https://github.com/TriForceX/MiyooCFW/wiki/RetroArch-Setup I think you should be able to download a core from this place https://buildbot.libretro.com/nightly/dingux/miyoo-arm32/latest/ and just put it into the cores folder in RetroArch on your device. But there might be additional steps needed to integrate them into the system, not sure at this point. BTW you should have added the name of the device into the post title. Such generic titles aren't helpful.

I have used already the cfw for this model https://github.com/TriForceX/MiyooCFW/actions/runs/4988520114

For GUI, SimpleMenu lets you change the UI to something more familiar from modern devices than with GMenu2X's themes. My favorites I use on it are ArtBook and MinUI. My hands don't really feel cramped when playing on the V90. I can cup my hands around the bottom of the device when I don't need to use the shoulder buttons, and if I need to use them, there's the option of rebinding the shoulders to the face buttons. I'm not really playing games on the V90 that would heavily need them anyway.

I really like the SimUI theme, whose github can be found here.

Please read the main page: https://github.com/dkodr/SimUI