Thank you, you saved my day! I am trying to install proxmox 6.2-1 in a virtualbox guest machine (for a teaching scenario). I have set virtualbox display memory to maximum (128MB) and yet proxmox seems to think that the hardware (virtualbox) can only display 800x600. No, I didn't enable EFI. There is no such problem if I use kvm. It seems to be
a bug of virtualbox
One note: in my case I see that the file generated by "Xorg -configure" is /xorg.conf.new (placed in the root directory).
Another note: the comment function in your blog seems not working.