You can process these with bash string manipulation alone, but sed and awk will do this pretty easy.

just like ssh -X

No, that’s not what’s happening. X11 forwarding is telling the server to treat a TCP socket as a display, and after passing xauth, the frames are just shoveled into an ssh session. Waypipe is serializing Wayland messages so they can be redirected to multiple portals, specifically over a socket. They don’t really work the same at all.

I didn’t know XFCE supported Wayland

Some parts of xfce do, xfwm4 does not.

so I casually ran vncserver, which launched xfce4-session

This is because your vnc is configured to do so.

except that it attached itself to the Wayland display (proxied to my local machine) rather than X display of TigerVNC. And here come the full XFCE right to my local machine (which is running Plasma).

This part doesn’t make a lot of sense.

If invoking xfce4-session works, it means you are doing so over vnc, not waypipe.

All of this produces a feeling of anguish… Maybe I cannot stand knowing that this could be the standard everywhere.

I have similar feelings about the lack of alcohol taxation and the low rate of rice cooker adoption in the west.

You are struggling to accept the imperfect world as it is. You should stop introspecting on the symptoms and try to figure out why you are unhappy with other people’s choices.