IGPU Frequency stuck at 0,40 GHZ

[silvercircle]

Is there any reason why my IGPU is stuck at 0,40 GHZ?

I read all I can find (FAQ.IntelHD.en.md, Opencore installation guide, Google,...) but no solution.
4k YouTube video's stutter, lower resolutions are fine. I'm almost certain that it is related to this frequency limit.
When I uwe the dGPU everything is smooth.
Catalina was fine when using Edge or Chrome because they did not use the IGPU to decode, on Big Sur they do use the IGPU.
I can of course turn it off (I have no display connected to it) but wonder why I can't make it work.
I'm on OpenCore 0.6.8

 

[Edhawk]

Why are you expecting the IGPU to up its performance and undertake any graphics work, when you system is set with a Headless/Empty framebuffer? Your AMD Vega 64 is set to undertake most graphics functions, bar Quick Sync and some compute processes. As I see it your IGPU is doing what it is supposed/expected to do.

Here is a sample of the output from Intel Power Gadget for my iMac1 system, the IGPU frequency hardly gets above '0' and not for any extended time even when the system is underload with multiple browser tabs open playing videos.