Apart from the Samsung Viewfinity that another commenter mentioned, there's also the LG Ultrafine 5K and the Huawei Mateview. The MateView is nicer than other 4K monitors because it has a taller aspect ratio of 3840 x 2560 so the extra 400 pixels of vertical space is nice for productivity work, although of course this is still fewer total pixels than a 5K display.
I bought mine like 2 years ago and it's been rock solid. IIRC they had some revisions over the years. And being rock solid: that's a bit of a lie because the monitor is wobbly as hell. So I've propped it with two supports on each side. Apart from that, the picture is the nicest I ever had from a monitor, and I had a lot of good ones. Text is super sharp and has acres of pixels. Compared to 4K monitor I can have both a terminal client and a browser side by side all looking nice. Can't fit that on 4K unfortunately.
