Comment # 42 on bug 1218948 from Christian Wittmer

(In reply to Takashi Iwai from comment #34)
> OK, then the original issue of Christian's machine is completely different
> from others.  The problem for others is about a regression of ax88179 driver
> (the actual crash), and this was already fixed in SLE15-SP5 git branch. 
> Meanwhile, your problem seems related with i915 graphics driver.
> 
> The hangup detected by the watchdog might be related with the firmware
> loading of i915.  Could you try to boot with i915.enable_guc=0 boot option
> and see whether the problem still happens?  The kernel warnings might still
> appear, but the hangup could be avoided by that.

I added it here to /etc/default/grub:
GRUB_CMDLINE_LINUX_DEFAULT="splash=verbose preempt=full mitigations=auto
security=apparmor i915.enable_guc=0"

I don't see the problem as long as a display is connected while booting.
If there is no display connected, it does not boot.
see /var/log/messages (2024-02-07T13:42...)
I will attach another one.
Even if I connect a display to see what is going on I do not get a screen.
Need hard power off.

Any idea on how to make it boot without display connected ?
Thank you