Some design choices of Wayland are really weird.

That said do you know of the wlr foreign toplevel management protocol? A lot of the smaller compositors support it. But yes a lot like e.g. Mutter and I think kwin do not.

everything you could want and more already was dreamt up and has a PR for it, you can thank Gnome for stonewalling everything for half a decade or more

Best option right now are to use the following protocol extensions

https://wayland.app/protocols/xdg-activation-v1 this extension covers your setting focus needs, but getting a list of other wayland clients is a bit trickier.

https://wayland.app/protocols/ext-foreign-toplevel-list-v1 this extension can list clients in theory, but its missing support for both gnome and kde.

Some of the unstable extensions have wide adoption, so perhaps take a look at each of them to see if they provide the functionality you want. Good luck!

Edit: was curious and did some more digging. KDE has their own protocol extension for this https://wayland.app/protocols/kde-plasma-window-management

As for gnome, I couldn’t find anything that seemed suitable, other than writing a gnome extension specifically to support this. I imagine that doesn’t fit within your vision for your project though.

Anyway, I had fun looking into this. Once again good luck!

There's probably a PR or a thread somewhere with a bunch of very angry nerds fighting over whether this is even a useful feature and there’s no API because they can't reach a compromise. There is no design.

Some wise people said that it was originally designed for car infotainment. Everything else is an addition.

I would imagine part of this is because multi seat (or cursor) wayland is just as important as single seat wayland.

Congratulations you have discovered the new hotness being forced upon Linux community (only 17 years in development and counting lol) isn't so hot.

My favourite quote from the linked article:

"Instead of providing a better way of doing something, common features are not supported at all, and instead it's the job of everyone else in the ecosystem to agree on a standard. That's not a stunning argument in favor of replacing something that already exists and that has already been standardized in X11!"

citation -

Wayland set the Linux Desktop back by 10 years

https://omar.yt/posts/wayland-set-the-linux-desktop-back-by-10-years

I just made the spicy decision to implement hyprland IPC in my window manager...

IIRC Wayland is only a spec, compositora are the implementation. I believe Wayland has a reference competitor, maybe target that?