If you encounter just Webfinger to be unknown/not set properly, it might be that you just installed Social beta 0.6 which has an issue there – took me a while searching for the general issue with .well-known until I noticed "Exception": "OCA\\**Social**\\… in the log:
{
"reqId": "B7mbg4cEvTPFnBY1e4LL",
"level": 3,
"time": "2023-02-03T18:22:00+01:00",
"remoteAddr": "78.94.68.73",
"user": "nursoda.admin",
"app": "index",
"method": "GET",
"url": "/index.php/.well-known/webfinger",
"message": "Actor not found",
"userAgent": "Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/109.0",
"version": "25.0.3.2",
"exception": {
"Exception": "OCA\\Social\\Exceptions\\ActorDoesNotExistException",
"Message": "Actor not found",
"Code": 0,
…