Server Version#: any (for at least a year or so now)
Player Version#: web
When following the support steps of the support article Authentication for local network access it will only work as intended when visiting the Plex server using the numerical IP address i.e. http://192.168.91.10:32400/web.
It will redirect to https://app.plex.tv/auth if we visit the local server via domain name.
I.e. http://myplexserver.mydomain.net:32400/web will reach the Plex server. However, it will not bypass authentication as instructed by the support article but instead re-direct to a webpage that is unreachable when there is an internet shortage.
I strongly suggest to set up the embedded web server properly and in the meantime to update the support article with a quick note, so people like me do not lose their minds over this issue.