https://github.com/neonkore/waypipe proxies Wayland over a network. It’s straightforward enough in theory: Wayland core is just a communications protocol plus shared memory; so you just need to forward the messages, and detect and send changes in the shared memory. Not the cheapest thing, but perfectly tractable. Of course, there are also more difficult extensions, like GPU integration, but that sort of thing was a problem for X as well.

This is how modern x11 worked too since nobody uses software rendering with x primitives anyway.