I have an RX6800 and an LG42C2, I installed the kernel using the AUR package, on Arch Linux.
Display is working, but I'm stuck on 420 8bit in 4K 120hz VRR, as with the stock kernel.
Here is the dcn_regdump. I could not detect my DCN version, so I guessed 3.0.3
dcn_regdump.txt