EWM implements a Wayland compositor as a native thread spawned by a dynamic module in Emacs, it's a full compositor within the Emacs process: https://codeberg.org/ezemtsov/ewm

So it is architecturally possible (but infeasible in plain Emacs Lisp).

For river (the thing this article is about) I wrote an Emacs WM, but also opted for a dynamic module for the Wayland protocol parts: https://code.tvl.fyi/tree/tools/emacs-pkgs/reka

This one could technically be written in plain Emacs Lisp, but I'm happy to use something that already has all the XML codegen stuff for Wayland figured out. Dynamic modules work pretty well, fwiw.