MacOS has a built in 4x4 window tiling which works for this purpose for me. I don’t find ever wanting more than 4 windows open on an ultrawide. Definitely not as powerful as something like xmonad but useful for the majority of my use cases.
Obnoxiously, it's part of the recent trend of overloading the Globe/Fn key, so it's hard to do with third-party keyboards.
Saner defaults would be better.