XDG-URL is a custom URL that represent the installation method of
desktop stuff.
Just click an XDG-URL link, or type XDG-URL in browser's address bar.
If you use Firefox, a program selection window opens the first time
you open XDG-URL, and you can choose "xdgurl" as custom URL handler.
If you don't get the program selection window or you are using
another browser, please set the xdgurl program as custom URL handler
for xdg:// scheme in the browser's settings.
From CLI, execute xdgurl program with argument XDG-URL:
$ xdgurl "XDG-URL"
426e7bc4f4