Im having the same problem with not formatting the site when coming from my external site.
I have looked into my router config but haven’t seen anything strange.
I have also tested with Edge, Firefox, Cromium and Crome with the same result.
Errorlog
Crome
Webbadress Description
…block-library/style.min.css?ver=5.7
(localhost) Failed to load resource: net::ERR_CONNECTION_REFUSED
…block-library/theme.min.css?ver=5.7
(localhost) Failed to load resource: net::ERR_CONNECTION_REFUSED
…twentynineteen/style.css?ver=2.0
(localhost) Failed to load resource: net::ERR_CONNECTION_REFUSED
…js/priority-menu.js?ver=20181214
(localhost) Failed to load resource: net::ERR_CONNECTION_REFUSED
…js/touch-keyboard-navigation.js?ver=20181231
(localhost) Failed to load resource: net::ERR_CONNECTION_REFUSED
…js/wp-embed.min.js?ver=5.7
(localhost) Failed to load resource: net::ERR_CONNECTION_REFUSED
