I have been getting the “Your web server is not properly set up to resolve” messages for quite a while, I spent a long time searching through the forum, and while I found other people’s problems relatable, I found very few actual solutions - most people just put a link to the documentation WHICH ISN’T ENOUGH - we wouldn’t need the forum if the documentation answered everything, would we? One person even just put a link to a search in the forum for the warning - not a link to a solution, just a link to a list of MORE THAN 50 PEOPLE with the same problem. OBVIOUSLY this is a a serious issue - a lot of people are asking about it. OBVIOUSLY the documentation is insufficient. And OBVIOUSLY the existing forum posts fall short of answering all the questions.
HERE IS HOW WE SOLVED THE PROBLEM:
On Ubuntu, I went to the .conf file for my site in /etc/apache2/site-available and within the <VirtualHost *:443> section I added
Header always set Strict-Transport-Security
Redirect 301 /.well-known/carddav /nextcloud/remote.php/dav
Redirect 301 /.well-known/caldav /nextcloud/remote.php/dav
Redirect 301 .well-known/webfinger /nextcloud/index.php/.well-known/webfinger
Redirect 301 .well-known/nodeinfo /nextcloud/index.php/.well-known/nodeinfo
Is this ideal? I have no idea - but it worked. And now that I’ve posted an actual solution I’m sure I’ll hear plenty of negative feedback about how people “would have been helpful if…” - and it is all BS, you weren’t helpful with the last person that had this problem, you wouldn’t have been this time either. Hopefully this post comes up in the search results for all the future troubleshooters experiencing this same issue.
Thank you to Stefan at https://strobelstefan.org/2020/03/02/nextcloud-und-das-laestige-problem-mit-well-known-caldav-well-known-carddav/ for getting me most of the way there.