I am happy to test. I tried 2 GBA games, Fire Emblem and Kirby & The Amazing Mirror. Both have choppy audio and are in slow-motion. My previous OS image is the community image from here: Custom D.E.O.T. V2.0+/Clockwork OS v0.5 image - With customised DEOT interface, Kernel 5.7, Optional 1400MHz OC, Debian 10 Buster, Retroarch 1.9.0, Mupen64+ plus more! (Current build: 200903)
The configuration from that image seems to work a lot better. I have the beta image on a spare SD card so I can try anything you want.