Hello Maldon,
I got back to Sequoia experimentation after updating my Motherboard BIOS, upgrading to NVMe drive and with the new GPU (RX6800XT). With this configuration and setup, your recommended EFI (SSDT-CPUR) for AMD worked like a charm. The only thing I had to change is a single boot argument, alcid=5 to get my Realteak S1220A working. The only problem I got is the Ethernet, there is just no way I can get it running after all I tried online.
Motherboard is Asus Rog Strix B550-F Gaming with the Intel I225-V. I didn't really touch your AppleIGC.kext and with the e1000=0 it boots just fine and it seems that macOS detects it everywhere, but it just won't work. It shows green in the network settings but it refuses to function, even when I pull the cable out, it still shows connected. It behaves really weird. Is there a way to make it work or anything else I didn't try? Here are few screenshots: