Oh! Thank you for highlighting this better. That's definitely not LCD inversion, and that's definitely not video cable.
This specific category of clustered glitch is typically framebuffer memory behavior --is never the cable; I would not 100% confirm monitor either.
- This may be a GPU RAM defect;
- This may be a monitor-overclocking defect;
- Etc.
But here, I'd think it's the monitor, yes.
A framebuffer memory "cluster of glitches" corruption is usually either in the framebuffer on the GPU, or in the frame buffer in the monitor (the refresh cycle buffer). A lot of it is benign (like "CGA snow").
It's my understanding that this monitor you have is a fixed-Hz monitor (without VRR). Fixed Hz monitors are sometimes extremely picky about refresh rates before glitching, so using a refresh rate that behaves better, can solve the problem.
If it disappears at 75Hz, you're probably OK. It's /usually/ harmless, especially if the display is not VRR-compatible. You could also try to permanently turn on/off VRR and see if it works better. Monitors have had a history of glitching weirdly at unexpected refresh rates (whether fixed Hz or diferent VRR maximum Hz). Even 74.9fps with a better-tuned VRR max of ~75.000, can become better than 74.9Hz native, because of the way scalers/TCONs are designed. It's not always the case, but I've seen this type of thing happen -- sometimes it's a memory wait-state glitch or a monitor framebuffer DRAM refresh glitch due to unexpected clockspeeds etc. Like a modern-day equivalent of 1980s "CGA snow" effect.
If it bothers you that much -- you may have to consider another monitor. While you're at it, a higher refresh rate (120-240Hz) is still great for productivity, even if you never game. Dell recently added 120Hz to one of their office monitors, and many Mac's now come with 120Hz as high-mainstream standard. And FreeSync/GSYNC performs better when min,max Hz is a 2.5x difference. (e.g. 48-120Hz VRR is considered the minimum range I recommend if you ever use VRR -- because even 50-70fps VRR is much smoother when Vrr(Max) is 120Hz).
However, if you never see it at a new custom refresh rate, I think you've possibly fixed your problem. Don't waste time on cables anymore -- I'd put my money on the monitor framebuffer glitching occasionally (etc) -- but I have almost never encountered a completely bug-free monitor. If you completely fixed your problem via a custom 75Hz mode, I would just cease to worry about it.
Don't forget to check for firmware updates that might fix this problem; your monitor latest firmware would be Version 1014.0 0.88 released by Samsung on Nov 29. 2023, according to
Samsung's Latin America website. Keep in mind that the chips running inside a 2020s monitor is more powerful than a year 2000s computer!!!
Are you running the latest monitor firmware?