An additional info: I just tested the latest version of ownCloud client for macOS (v2.2.4.3709): same behaviour. I missed to point that I’m running Nextcloud 10.0.1 as server.
As further explanation, I’m working with Nextcloud to rebuild what was known as “Mobile Account” feature (aka PHD, Portable Home Directories) which has been killed by Apple in its latest macOS release. I’m at a good point, but I absolutely need nextcloudcmd authenticate by using the same stored credentials used by the GUI client.
In the mean time, I’m running nextcloudcmd with the -n switch, and I’m pleased that the .netrc auth method works, but it’s not a viable solution for production use.
I renew my offer to sponsor the work of whoever will be able to make that working.
Thanks again.