I have very occasionally seen something similar only after upgrading from F42 KDE, you could try changing adaptive sync to always as suggested here (and elsewhere online) for a somewhat similar issue Weird pixelated glitches on my screen after installing fedora on my new laptop - #2 by Andy_Coder . I also had issues on older versions of Fedora when EDR (Extended Dynamic Range) was active so you try changing that setting too. I think hardware is less likely the issue, you could try a live disk of another distro to get some insight.