from firefox itself, browse to
about:preferencesand click the “Set default” button
Does not work. Does not do anything other than silently fail. Chrome continues to be the default browser.
xdg-settings set default-web-browser firefox_firefox.desktop
Does not work. Again, it just silently fails to set firefox as the default browser.
Did you try your suggestions before responding? My test procedure is: double click *.html file on the desktop, see what opens. For me, it’s Chrome, even after your suggestions. Therefore, these suggestions do not work, and therefore the title of the post is not misleading … firefox SNAP can’t be set as the default browser.