There don't seem to be any other references to fbturbo or Allwinner in the remaining configuration.

Then I don't understand from where the fbturbo configuration is referenced.

Can you check if the file still exists after you remove the xserver-xorg-video-fbturb package ? If so, remove it and see if - after rebooting - you still get the error.

I'm trying to install retropie on armbian bullseye on a oprangpi+ with this script, but the package "mali-fbdev" is missing!

You have this package?