I come to my fellow Kiwis as a last resort. I need help fixing my niche use-case issue that I cannot find info on anywhere else online.
I live in a tiny studio apartment and I've got my desk set up in the corner with my PC. No issues there, everything's golden. However, when I game I like to do so from the couch in front of the TV I spent too much money on. So naturally I have an HDMI cable connected to my TV as well as my monitor. The problem is that when I have my GPU connected to my monitor and TV at the same time, I experience lag and stuttering. Not just while gaming, even scrolling through a web page will stutter and hitch. There are no problems when it's either just the monitor or just the TV connected.
An astute Kiwi will say "well, just don't have both connected at the same time." And they would be correct. That fixes the problem, but my weapons-grade autism will not accept this. In my mind, there shouldn't be a reason I can't enjoy my PC while it's connected to both my monitor and my TV. It is simply ridiculous and I won't accept it. Both are set to the same refresh rate and resolution, so save your breath if you think I haven't tried the obvious fixes. The problem persists even if my monitor or the TV is turned off, which further perplexes me.
I'm on Arch, but I don't know how much that matters because this happened when I was using Mint earlier. It happens with both an Nvidia and an AMD GPU so drivers probably aren't the problem. It does not happen if I boot into my Windows drive, which leads me to believe the problem is somewhere with Linux