OpenGL issues in graphics mode result in blank gdm screen

Hi,

I'm running a debvm from an arm64 Raspberry PI, using RaspberryPiOS / bookworm, and debvm bookworm-backports.

debvm passes:

                 *)
                               -device "virtio-gpu-gl-$TRANSPORT" \
                                -display gtk,gl=on \

GDM results in a blank screen with warnings like this on the host terminal:

(qemu:364870): Gdk-WARNING **: 16:15:12.265: gdk_gl_context_set_required_version - GL context versions less than 3.2 are not supported.
GLSL feature level 140

Dropping gl fixes the situation:

                *)
                                -device "virtio-gpu-$TRANSPORT" \
                                -display gtk \

Is there something to fix wrt OpenGL, or should we introduce a way to disable GL graphics?

Note: I see that RaspberryPiOS/trixie is eventually out, I may retry with that later.