It can be convenient to start eww directly from the command line. The
eww-browse
function can be used for that:
emacs -f eww-browse https://gnu.org
This also allows registering Emacs as a MIME handler for the ‘"text/x-uri"’ media type. How to do that varies between systems, but typically you’d register the handler to call ‘"emacs -f eww-browse %u"’.