I'm using the U3219Q at 1:1 resolution (so 3800px wide) on BigSur and Monterey, and some display text is sharp at the beginning and end of the text block, but fuzzy in the middle. It's like there's an aliasing going on, where a text block that would be natively 100 px wide is shown at 99px or 100px.

It was better on previous versions, I think Mojave was the last good one.

Yeah, I was completely surprised when I moved from Ubuntu 20.04 to MacBook Pro 14 on the very same Dell U3219Q: MacOS made text editing completely unpleasant.

Then I upgraded my son's laptop to Ubuntu 22.04 RC, and I was greeted with the same fuzziness. I hope that's only due to Wayland, I haven't tried out the X desktop when docked.