It works for me now, but I don't know the cause. For me dGPU's vfio binding plays a role.
To reproduce solution:
- removed dGPU from server and pluged hdmi to iGPU
- removed files in /config/modprobe.d/ [i915.conf] [ast.conf]
- removed file /config/vfio-pci.cfg
- kept plugin "Intel GPU TOP" installed
- started server -> checked iGPU with "intel_gpu_top" in terminal -> iGPU working
- checked if /dev/dri is existent. -> OK now
- shutdown server and pluged in dGPU again. HDMI connected to dGPU only.
- started server and checked iGPU with "intel_gpu_top" in terminal -> iGPU still working
- also started VM's and checked dGPU passtrough. -> working (without[!] using vfio binding via "tools->system devices")
My initial situation was:
- vfio binding used for dGPU passtrough to VM (thought it is necessary. But seams not.)
- iGPU activated via bios. Multi-Monitor enabled
- intel_gpu_top shows nothing
- no /dev/dri/ available