I have a 49” monitor and tried Niri for a while. I had some issues regarding Wayland, I believe because of Nvidia and stopped using it. I could probably solve them, but I have been using X since years and I don’t feel switching right now.

Anyway, for that short amount of time I liked most of it on my ultrawide monitor. Except when you open just one application, it stays on the left-most part naturally and it honestly sucks to look at. I have no idea if I could modify the settings to launch apps with an offset and eventually occupy the complete screen estate. I‘m planning to build a new AMD machine and will try Wayland compositors again for a longer period of time. Niri is my first candidate.