As a 1080p 21' monitor user, when I got my first Mac laptop seeing it's HiDPI sharp text I was instantly hooked. Thing is, I still need to do my work on a PC. So I started my search for a higher resolution than usual monitor.
Recently, Dell dropped s2725qs which is a steal at 300 euros. It's 4k 27 inch 120hz and 99% SRGB. I set it at 150% scale on KDE Plasma. It works well. Compared to Cinnamon where text was a bit fuzzy at 150% (fractional scaling duh...). Optimal scenario would be 5k so you can use 200%, hence no fractional scaling, but you can't complain at this budget. My eyes are really happy now. I love it. Speakers are surprisingly decent. 120hz is very nice addition, actions like scrolling or playing a game make it so enjoyable.
I know this is technically not a HiDPI monitor, since they start usually at 200+dpi. This Dell is 161dpi, but works for me.
If you have any questions, let me know!
My first big monitor was a 32" 1440p one. I used it on 100% scaling and I could see some pixel on that if I really tried, but the size I can't go back on. So my next and current one is a 32" 4k one. It needs a higher fractional scaling though, but Plasma handles is really well even with a secondary monitor at a different scaling.