Problems with FULLSCREEN 640x480 on Ubuntu 20.04?

Hello,

is anyone having trouble with fullscreen on Ubuntu 20.04?

I’ve got completely black screen after updating to Ubuntu 20.04 (from Ubuntu 18.04) (non-fullscreen though)

Fullscreen feels choppy when I switched from Linux Mint 19 to 20. Windowed mode is fine. Also I’m using openGL directly.