It is supported.
I have a 6700XT, ryzen 5800X on a x470 MSI Gaming Pro Carbon and SAM is working.
Check that your motherboard is on the latest BIOS and enable re-BAR in BIOS.
Also you must have UEFI bios enabled because it's not working on CSM legacy bios. If you are on CSM BIOS than it's more complicated to enable UEFI BIOS...I think that you have to reinstall windows. ( or it may be a workaround but I don't know it)