hmmm. not good news. time for you to do some troubleshooting. try changing the port on the video card, changing the video cable, try using the video port on the motherboard. if the problem persists, then it is the monitor problem.
2580 x 1080 sounds way too small for 34" monitor. I run two 27" QHD monitors unscaled and I think that's the ideal size and resolution for my purposes. I would not mind trying dual 4K 34" monitors unscaled, but think that might be too much screen.
I'm a fan of the 38" Ultrawide 3840x1600 - just that little bit more real estate to work with, but I do also have a 27" flat monitor rotated (so 1440 x 2560) for those "long" page documents - both Nano IPS panels from LG. When you first get the ultrawide monitors, charts seem a little distorted but that goes away after a few weeks. What you really want, for best image quality and app compatibility is 100% font sizing at the highest PPI that your eyes can handle. You can run at a different resolution that native but you'll get some interesting interpolation artifacts (fuzziness). However, if all of your apps seem to handle font size scaling correctly then you can go for a higher PPI, but that's rarely the case in my experience. Here's some PPI for common resolutions/sizes of monitors (and TVs). 68 PPI 65" 3840x2140 (aka 4K/UHD) 70-73 PPI 32" 1920x1080 (aka Full HD) 60" 3840x2140 (aka 4K/UHD) 80-82 PPI 27" 1920x1080 (aka Full HD) 34" 2560x1080 49" 3840x1080 (aka 32:9) 55" 3840x2140 (aka 4K/UHD) - this is coming out in Samsung Odyssey Ark 88 PPI 50" 3840x2140 (aka 4K/UHD) 93-96 PPI 32" 2560x1440 29" 2560x1080 104-110 PPI 27" 2560x1440 34" 3440x1440 38" 3840x1600 43" 3840x2140 (aka 4K/UHD) 49" 5120x1440 55" 5150x1440 117 PPI 75" 7680x4320 (aka 8K) 125 PPI 70" 7680x4320 (aka 8K) 135 PPI 65" 7680x4320 (aka 8K) 140-147 PPI 32" 3840x2160 (aka 4K/UHD) 60" 7680x4320 (aka 8K) 160-163 PPI 27" 3840x2160 (aka 4K/UHD) 55" 7680x4320 (aka 8K) 218 PPI (aka Apple Retina) 27" 5120x2880 (Apple Studio Display) 32" 6016x3884 (Apple Pro Display XDR) 280 PPI 32" 7680x4320 (aka 8K) Beware of the chroma subsampling limitations of using many TVs as a computer monitor - this will result absolutely horrid text quality - make sure your TV has chroma 4:4:4 support (and have configured your TV to handle it - some require explicit configuration). So, Baron's eyes are favouring more of the 82 PPI area. I have a colleague that struggles with anything beyond 70 PPI.
These types of questions about monitors and computers that pop up every so often are kind of silly and trivial. Just get what you want, and be done with it....so you can truly focus and refine and understand your trading and make money from the market. Focus on the true, bigger, real picture, overall, ahead...and not get distracted by smaller ideas and concepts.
I had used different monitors and layouts until recently, so should have nothing to do with the motherboard or card. I initially thought maybe it is unique to ultrawide screens to sorta synchronise the pixels, but then it doesn't make sense...might switch from hdmi to displayport and see later
Many HDMI cables are not up-to-spec. LTT did a test on 53 cables from 17 manufacturers. 9 failed. Not great odds! Definitely worth trying a different cable/brand and make sure it's HDMI 2.1 spec (or DisplayPort).
Better to just use hidpi scaling, like a 1.25 multiplier so you get a crisper image compared to modifying resolution. For me the absolute max for 1080p was 24", using a 1440p (2560x) 27" now, for 34" you'd probably go for 3440, it would be right at the limit with 2560.
I've had the Samsung curved extra wide monitor for about 4 years and a few months ago it started doing the same... Goes to black long enough for me to say WTF in the middle of my gaming. However, it stopped doing it lately and wonder if it's a driver update that resolved the issue..