Someone else also said to update the firmware to 138.0.0.0, but I'm on 144.0.0.0.0 and I still have the issue (or can I only access that firmware in Mojave?)
I never saw the flickering when he played Minecraft on Mojave. I could update to Mojave, but my dad (who was the previous owner and is the tech guy in my family) said that he had a lot of problems and glitches on there. The difference was that they said that if you restart or put in the original graphics card and restart it should fix it, but it doesn't for me). Also, when I use Parallels and play games on Windows, the issue is gone (it was the same case for someone else who had the problem. My problem is that whenever I open OBS or a game (like Minecraft), the screen (even if the game is in windowed) will flicker every few seconds, making it really difficult to play. It's currently on High Sierra (I'm not sure about the exact version, but if anyone wants to know I can look).
Flickering screen/artifacts on 2009 Mac Pro I have an Early 2009 Mac Pro (with the firmware flashed to 5,1) with an rx 560 graphics card.
