And on Amazon; don't think it's widely available anywhere else, unfortunately.
Ignore any commentary about Windows support, because unless something has changed recently, it has poor support on Windows and is missing most features. I have heard mixed things about whether it only supports Freesync on Linux rather than Freesync or VRR. Since my TV supports both and there doesn't appear to be a way to reliably differentiate between the two, I can't confirm either way.