Okay, I had heard of “River” before but I was not aware of this:

https://codeberg.org/river/river

River defers all window management policy to a separate window manager implementing the river-window-management-v1 protocol. This includes window position/size, pointer/keyboard bindings, focus management, window decorations, desktop shell graphics, and more.

This sounds promising and it follows the old X11 model. River does all the nasty Wayland work and I can make just the WM? 🤔🤯