Dell Precision 7520 with an AMD GPU. The degree of flakiness is different depending on whether you're on Plasma or GNOME, but it's there nonetheless.
I switch between a station that has a 4k display next to a standard 1920x1080 display as well as my laptop display (3200x1800) and my home setup with the laptop and 2 4k displays.
I had an issue on the 4k displays when I attempted to run two displays and a usb hub on a single thunderbolt line, but that wasn't Wayland, that was me being dumb: The thunderbolt protocol only support 40Gb/s and each monitor uses 20Gb/s and the hub eats another 10Gb/s. If the hub got detected last, it dropped to usb 2, if one of the monitors came online last, it would drop to 30hz refresh rate. Frankly - I was a little floored when I realized that I was the one being dumb and the system was mostly still just making things work. Just for shits and giggles I booted up an x-session after to see what it does. The answer is lots of black screen.
Moreover: when I pass through the dGPU to a virtualized macOS, all monitors I plug in just work!
How does X work on that setup?
Mixed scaling? Is that that thing when you open chrome and it’s blurry on your hidpi monitor?
It's a painful first compile, but the only issues I've hit have been a few menus in the extension debugging screens that are too small.
On Wayland I get excellent multi-monitor support (mixed scaling ratios, much better automatic detection and configuration, much better plug-and-play). I also have a touchpad on my XPS that feels just as good as a Mac.
To boot, I haven't had to touch a config file related to input devices or output devices a single time using Arch/GDE/Wayland.
Honestly, I'd probably still be running linux in a VM on my laptop if it weren't for Wayland.
If X is your opinion of "stable and working" then I don't want any part of your systems.