I never got it running. And I tried everything: ipvlan, blacklisting i915, install Intel-GPU-Top, with Plex docker an without, HDMI dummy plug, and a thousand other tips.
The hardware was totally fine because I had no issues with Windows, Truenas scale, proxmox, batocera, etc.
In the end I sold the NUC (NUC 11 i5) and switch to a Ryzen based Mini-PC. As of today I have 72 days uptime without any issues.
It seems like Unraid and Intel integrated graphics are not a good combination.