The RX6600, RX6650, RX6800, RX6900 and RX6950 (including the XT variants) are supported in recent macOS releases, Big Sur, Monterey and now Ventura.
These supported GPU's use either the Navi 21 or Navi 23 chip.
These specific cards are supported in macOS because Apple have added drivers for the following Radeon Pro II cards, for use in their Mac Pro 7,1:
- W6600
- W6800
- W6800X
- W6800X Duo
- W6900X
The desktop variants of these Workstation GPU's use the same chip, so support is provided natively by Apple.
None of the other RX6000 series cards are supported, i.e. RX6400, RX6500 or RX6700 (including the XT and 6x50 variants).
These unsupported GPU's use either the Navi 22 or Navi 24 chip, which none of the Workstation GPU's use, so no support.