[SOLVED] QEMU/KVM - X11 won't start - Ubuntu 18.04 both host and guest

Guest X11 will start fine when running live-boot, but will not start from installed image.

I'm running Ubuntu 18.04.2 with QEMU 2.11.1 (the Ubuntu package).
I'm trying to run a virtualized Ubuntu 18.04.2 with the following command line:

qemu-system-x86_64 -drive file=/Groups/Virtual_Machines/java-desktop.img,index=0,format=raw -cdrom /Groups/Virtual_Machines/OS-ISO/ubuntu-18.04.2-desktop-amd64.iso -name JavaDev-VM -enable-kvm -smp 4 -m 8G -monitor stdio -k en-us -boot c

At which point, the GDM tries to start in a fast loop until it finally gives up, then (after about 2 minutes) I can Alt-2 -> Alt 6 and login command line. Exact same command line, I can end with -boot once=d and it will boot from the CD image, and I have no problems with X11. I can find no configuration differences between the running cd image and the no-X installed image (I've done recursive diffs on /etc/X11 and /usr/share/X11). startx also does not work.

The working, cdboot seems to be enabling a module called vbe

(II) Loading /usr/lib/xorg/modules/libvbe.so

The non-working, does not get that far. Both fail trying to use "fbdev", but only the cdrom run then loads VBE and tries that instead.

It feels like the X11.0.log files are too large to share here.

-rw-r--r-- 1 gvollink gvollink 142126 Jul 12 00:27 cd-Xorg.0.log
-rw-r--r-- 1 gvollink gvollink 7933 Jul 12 00:26 fail-Xorg.0.log

But, EE from the working one...

cd-Xorg.0.log:[ 53.550] (EE) open /dev/dri/card0: No such file or directory
cd-Xorg.0.log:[ 53.550] (EE) open /dev/dri/card0: No such file or directory
cd-Xorg.0.log:[ 53.551] (EE) open /dev/fb0: No such file or directory
cd-Xorg.0.log:[ 53.552] (EE) open /dev/fb0: No such file or directory
cd-Xorg.0.log:[ 53.553] (EE) Screen 0 deleted because of no matching config section.
cd-Xorg.0.log:[ 53.553] (EE) Screen 0 deleted because of no matching config section.

and, EE from the failed one...

fail-Xorg.0.log:[ 88.340] (EE) open /dev/dri/card0: No such file or directory
fail-Xorg.0.log:[ 88.340] (EE) open /dev/dri/card0: No such file or directory
fail-Xorg.0.log:[ 88.341] (EE) Screen 0 deleted because of no matching config section.
fail-Xorg.0.log:[ 88.342] (EE) FBDEV(0): FBIOPUT_VSCREENINFO succeeded but modified mode
fail-Xorg.0.log:[ 88.342] (EE) FBDEV(0): mode initialization failed
fail-Xorg.0.log:[ 88.342] (EE)
fail-Xorg.0.log:[ 88.342] (EE) AddScreen/ScreenInit failed for driver 0
fail-Xorg.0.log:[ 88.342] (EE)
fail-Xorg.0.log:[ 88.342] (EE)
fail-Xorg.0.log:[ 88.342] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
fail-Xorg.0.log:[ 88.342] (EE)
fail-Xorg.0.log:[ 88.345] (EE) Server terminated with error (1). Closing log file.

The boot of the cdrom image does NOT have a /dev/fb0, but the installed boot does. Does the failure to find an fb0 lead to the cdrom to try the vbe module that ends up working? I don't think deleting the /dev/fb0 will work, but I think I'll try that next.

Disappointingly, deleting /dev/fb0 actually works, but the boot sequence recreates it, which is quite inconvenient.

So, boot.
Alt-F2 several times, until it shows up, but is blinking while GDM/gdm3 tries to initialize over and over again.
Wait about 2 minutes until the blinking stops (and GDM is simply given up).
Login text mode on VT2
$ sudo rm /dev/fb0
$ sudo systemctl restart gdm
GUI screen shows up.

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This is a resolution, but... not a very satisfactory one.

I created a service and script to remove this on boot. Systemd style.