Commands() is used as the only backend for Open(), but there’s OS-specific ways to open things in a browser instead. Sadly on Linux, it is complex:

1. Consult $BROWSER for a “:”-delimited list of executables.
2. If it’s unset or none of the executables can be found:
   1. xdg-settings get default-web-browser will return the .desktop file name, e.g. firefox.desktop
   2. Find that file in one of ${XDG_DATA_HOME-$HOME/.local/share}:${XDG_DATA_DIRS-/usr/local/share/:/usr/share/} (subdirectory applications)
   3. Parse the Exec line in that file and replace %s, %u and whatever with the file name/url/… to get a command line
3. Execute the command line you built from $BROWSER or the .desktop file
4. If all the above failed, fall back to xdg-open

As said, this is harder than it should be, but it’s the only way to do it correctly AFAIK. xdg-open does all this, but there’s no way to tell it “open the path/URL I give you with a browser”. If you e.g. want to open a SVG with a browser, you need to go the above route.