Fortunately we don’t have to flash the VBIOS. We can fix this with an SSDT. Is the 6900 XT installed in the first x16 slot (closest to CPU)?
Yep, one step ahead of you already

Found your post, put the SSDT in and BOOM, it's working!
My Geekbench GPU Metal score is 172.000, which should be how a well working card performs, correct?
I do have another concern regarding boot times though. It's currently around 7 minutes. I'm using a Samsung Evo 1TB M.2 SSD, which I've read is part of the problem?
I've taken a screenshot of the part of the boot which takes the longest. 2/3 lower thirds of this screenshot takes 5+ minutes. Any ideas?
Thank you so much
@CaseySJ ! Also, do you have a tip-jar or a Paypal or crypto address I could donate too? I feel like a leech asking you about all this for free.