These warnings about webfinger and nodeinfo drove me nuts.
It does not seem to be the case here, but since I found this through web search on my way to find a solution, I allow myself to add some additional info (that is not yet in the manual, at the time of this writing), so that others might find the cause quicker.
/.well-known/caldavand /.well-known/carddav are usually straight forward, but for the afore mentioned endpoints I always got the warning message despite the redirection working and the requests being handled by index.php.
Background: in order for any endpoint (other than caldav and carddav) to return a positive result, these endpoints need to be registered by an app. Otherwise, even if redirected correctly, index.php would return a 404 status code alongside the special response header x-nextcloud-well-known and the content {"message":"webfinger not supported"}.
For nodeinfo, the endpoint is handled by the social app which I had installed but not enabled. Hence the endpoint was not returning a 200 status code, but rather a 404.
The reason I got a warning in the Administrative Settings overview was that I had configured a special 404 error page in my web server. Hence, the special response header x-nextcloud-well-known was not forwarded to the client and the test would not recognize that the endpoint was indeed resolved correctly.
My PR for the documentation also contain some useful curl command to diagnose the redirection for
caldavcarddavwebfingernodeinfo- any other
.well-knownservice - and also those who should not be redirected
I hope this may help others to track down the issue they may face. Even it is not a custom error page, understanding the requirements for the test to succeed might be useful in finding the issue.