I have been able to get a clean installation of Ventura 13.6 up and running using NootRX.kext with a PowerColor Fighter RX 6700 XT 12GB card. System consists of Asus TUF Gaming B550 WiFi Plus motherboard, Ryzen 5 5600G CPU, 32GB 3600MHz RAM, Broadcom WiFi/BT card (reason I am still on Ventura).
As instructed by
@ExtremeXT I removed the agdpmod=pikera boot argument from my config.plist, as it is not required when using NootRX.kext.
Been messing around with different SMBIOS options started with iMac20,1, moved to MacPro7,1 both work perfectly. iMacPro1,1 SMBIOS gives a black screen after short Apple Progress bar, system is running but dual displays are black/blank.
Metal Geekbench scores are a little low on my system, but I am still trying to see if they can be improved. Started with iMac20,1 and 152K Metal score in GeekBench 6. I have now got it up to just under 160K using MacPro7,1. ExtremeXT's test with RX 6700 XT gave Metal score of 173K, so still a little behind but making headway with my own testing.
iMac20,1 score
MacPro7,1 score.
Other than the Black screen issue with the iMacPro1,1 SMBIOS I haven't encountered any issues in Ventura with the RX 6700 XT.