I get it work with URL https://my.domain.com/remote.php/dav/principals/users/USERNAME
I don’t know if it’s related but my NC instance is on OVH shared host : in most application, setting only https://my.domain.com/remote.php/dav/ does not work but full url with principals/users/USERNAME works much better
also, for webdav connexion, like with wincp, working url is https://my.domain.com/remote.php/webdav/
it’s quite messy… take me a lot of search, trials and errors to make everything works as expected (files, calendar and contact)