*ERROR* No UMS support in radeon module! when installing ubuntu

I'm trying to revive this old computer with windows 8.1 installed running very very slow. But when booting from usb, I got "blank" screen with just 1 color, and the color go changing. If I try to boot with safe graphics, I just got a glimpse of the wallpaper then this:

What I'm missing?

EDIT: starting ubuntu in safe graphics gives me this error:

[drm:radeon_module_init [radeon]] *ERROR* No UMS support in radeon module!

EDIT2: I was able to try-live ubuntu 20.04.1 y 18.04.6 but the colored blank screen appears after a few minutes...