The SSDT-6900XT is only useful if not using WEG. For months, I have used BS and now Monterey using only WEG and no SSDT file (for RX580, Vega56, Radeon VII and now 6900XT). Such SSDT files are not necessary for a boot if using WEG.
And even if not using WEG, while the SSDT is helpful in re-naming the GPU devices as seen in IORE, the computer will still boot without it. I done this many time on both Intel and AMD platforms.
If one wants to inject certain properties (like control the fan and GPU speed), these can be injected via an SSDT or injected by using DevProp section. The SSDT method is best, especially if one also wants to re-name devices.
Portion of SSDT code to rename GPU devices. That is, how it's done: bridge after DODF becomes EGP0 and next bridge becomes GFX0:
Result after above SSDT re-name as seen in IORE:
Result after re-name by WEG. The first bridge is not re-named, but this is only cosmetic and seems to have no impact on GPU functionality.
(Note: for those paying attention, this IORE taken from a different mobo than the above example, so the D0BF device is here D0C1, which would mean that the SSDT shown above would not work for this mobo unless changed, and it is for a different GPU and that portion should be changed as well.)