(xdg-open seems to be supposed to be the universal one...)

Also manually adding [Default Applications] x-scheme-handler/zoommtg=ZoomLauncher.desktop to either $HOME/.config/mimeapps.list or $HOME/.local/share/applications/mimeapps.list does not lead to xdg-open via exo-open recognizing the zoommtg protocol.

A solution is almost indicated in the question: hinder xdg-open from choosing exo-open. A brute-force approach is to copy /usr/bin/xdg-open to /usr/local/bin (/usr/local/bin is earlier in PATH unless PATH has been modified) and to patch it to use open_generic instead of exo_open (unlike the XFCE4-specific exo-open, open_generic does honor xdg mime types)

when the link of accessing a workspace appear I only get the popup: "Open xdg-open?" and then nothing happens.

neither knows what to do with naked domain. So gnome-open http://askubuntu.com works but not gnome-open askubuntu.com. Here is a small function to make it easier to type and accept the stripped down domain name. function go { gnome-open http://$1 ; }

There's a command that knows about your default browser: xdg-open http://google.com This will also work for every other type of URI (Uniform Resource Identifier), like images - which will automatically open with eog, openoffice documents, and so on, and also on filesystem paths (xdg-open /tmp/foobar.png).

xdg-open should do the same thing - actually, it will call gnome-open, or kde-open, or whatever, depending on your desktop environment. Thus it's more portable.

The advantage is that you can use gnome-open for almost all file-types, URIs and directories. It's one command to learn, instead of trying to remember about obscure commands like sensible-browser

XDG stands for X Desktop Group aka freedesktop.org

what does xdg stand for? Its hard to remember without knowing that.