AIUI xdg-open is the standard tool which then forwards to the (equivalent of the?) desktop-specific tools. For KDE it's `kioclient exec`.

I wouldn't be surprised the GNOME people try to break this standard tool too.

This is correct. Unfortunately, xdg-tools is a set of almost forgotten scripts that need some more eyes and collaboration to polish. I've seen many problems there. Nobody is actively maintaining it, but a couple developers could get the ball rolling. (I'm interested)