Well I'll be damned! AMD does seem to have up their encoder game with the Navi series onward.
They were rightfully called out as having pretty bad encoders before that though, which I personally experienced on an RX 480 I used to have in my system. It made parsec a bit blurry and added quite a bit of latency.
Also, I would stand by the recommendation to avoid older office PC's with AMD graphics, since none of them are going to have Navi graphics.
You still can, as far as I know! It's just that I don't think X would have the throughput for games. I recently learned about that functionality in a Cathode Ray Dude video, where he shows how it even got ported to Windows 3.11!