Any chance you can try another cable? Are you using an adapter?
I had an issue with a 6900xt and an older Samsung (10+year old) monitor I used for my 2nd monitor. I was using an adapter; display port to HDMI. It made it look a tad blocky. Went straight HDMI and it looked oddly similar to yours.
Tried a few different cables and nothing helped. Might be an issue with the new gpu and old monitor, hopefully it's something simple.
I ended up getting a new monitor as I couldn't fix the issue.