That is good!
In the meantime I have setup the Hetzner storage box with sftp and that works great. I consider sftp more secure because it uses ssh for authentication and encryption. Also, I have seen bad webdav performance for big files in a nextcloud environment. That does not need to be the case for kopia. But it gives me a bad feeling in general with regard to webdav.
Anyways, I have to say that I have dropped kopia. The “fix missing blobs” thread here in the forum convinced me that kopia is not as robust as restic.
Restic might be a little slower (I dont know) but it is much easier to handle and it really gives me a good feeling for data integrity in a remote repository.