How to passthrough integrated graphics on Intel NUC?

Hi,
I've been struggling trying to have the HDMI output of my Intel NUC BXNUC10i7FNK i7-10710U display the guest's screen (not talking about xorg, just kernel for now).

System:
Host: Slackware64-current w/ qemu 5.0.0 and virt-manager 1.5.1
Guest: Slackware64-current
Kernel on both: 5.4.58

What I tried so far:

• virt-manager PCI passthrough of the adapter ID as shown in lspci: 00:02.0 VGA compatible controller: Intel Corporation Device 9bca (rev 04)
• rmmod i915 in host
• intel_iommu=on and nomodeset kernel options in host, guest, and both

The further I could go is that the guest turns on the backlight of the monitor at some point in the kernel boot (very close to login prompt). But the screen is still black. Shutting down the guest immediately puts the monitor in blue screen (no signal).
This proves something is working, but there must be a last piece I am missing. What can I try?