That is the exact card I have and it is a great video card, though now may be more expensive to find unless used. Depending on what you want to spend, you can find a RX6600 for about 239, which is about what I paid for my RX580 about 4 years ago.
What BIOS loader are you using? I had High Sierra running on my computer using Clover, but when I went to Monterey I needed to go to OpenCore. It took me a bit, to get everything switched over, but it is much easier to do things with it once I got it up and going on Monterrey