What kind of iGPU do you have ?
With my AMD Renoir I have at times tried to completely disable the display, but usually I just avoid dom0 using it as a PCI device (through pci-stub.ids=...), on the premise that FB_EFI from dom0 should not prevent amdgpu from starting any more than its usage by the BIOS. I could be wrong, but at least I’m under the impression I’m indeed making progress, however small.
@ctr you don’t have persistent userspace logs, but there are still several saved logs if you manage to enter your LUKS key (for next boot if you had to do it in the dark or suffer other blocking issues):
- guest kernel:
/var/log/xen/console/guest-sys-gui-gpu.log - stubdom:
/var/log/xen/console/guest-sys-gui-gpu-dm.log - libvirt:
/var/log/libvirt/libxl/libxl-driver.logand/var/log/libvirt/libxl/sys-gui-gpu.log - dom0’s journal also sometimes shows valuable info
Aside from that, you can also setup a serial console if needed (managed to did that at one point, requires a bit of configuration).