I tried it yesterday. It works With RX6600XT, OC 0.9.3, latest kexts, SMBIOS iMac19,1.
First updated the SMBIOS from iMac18,3 to iMac19,1 (also updated SMBIOS in USBports kext)
Now I can access Sonoma beta in system update. I didn't wanted to risk existing Ventura, so tried to download full...