hallo,
i want that the user only can use the external storage for Uploading Files.
in the space directly on the NextCloud Server, the user can’t upload any files.
I don’t quite understand your question. But maybe you can solve the problem by giving the user a quota of 0 bytes.
Even if it doesn’t correspond to your question. But Group folders or Guests are very interesting in connection with 0 bytes (no separate Nextcloud area for the user).
Because of this post from you and the answer i think you can not set quota on external storage and deny access to Nextcloud storage. I think it is the same quota for the user. So my suggestion with 0 bytes will probably not work if you want also a quota on external storage.
Maybe the best way is to set the quota for the user to 0 bytes and use Groupfolders. You can set a quota on the Group folder. But then the data is not stored on external storage.
For small amounts of data, it shouldn’t matter whether the data is stored in Nextcloud or externally. In addition, processing directly in the Nextcloud is usually more reliable.