Hey everyone, im having similar issues, ok so first this first im on rpi4 latest retropie 4.8.
This was the only close issue i could find.
The thing i am having is my gamepad and keyboard wont work when adding XINIT to yabasanshiro emulator.cfg i tested running retropie on desktop but gets hot so i than thought why not reverse it, now all games should be running from vulkan from my understanding and run great but notging works i have to reboot my pi from ssh.
Could this issue be the same for fullscreen or maybe i need to point my config to my key2map for yabasanshiro.
Thanks