I want to transfer files to a new computer, including hidden files such as ~/.thunderbird and similar. My plan is to back up to a server from the old machine then restore files to the new machine via NFS to and from a server. Using Dolphin in superuser mode on the old client I can mount the remote directory (on the NFS server) but cannot copy files to the server. Dolphin says "Could not make folder /BUonK/.thunderbird/fzmmogm.default" for example. Permissions on server are set to let my account and all users modify files in the server directory linked via NFS to the mount point /BUonK on the client.
Tried rsync (via Luckybackup) which moved most files but not those in .thunderbird. Midnight Commander copies files as required, but is not "smart" about duplication the way rsync is supposed to be. Any hints on why Dolphin (and rsync) doesn't behave as I expect? Or do I not understand limits for file transfers?
OpenSuse 15.2 on all machines. Updated today.
Thanks in advance.

trying to make folders with / on a system using \ as a folder separator is usually bound to fail...

Running openSuse 15.2 with Plasma 5.18.6, Frameworks 5.71.0, Qt 5.15.2, kernel 5.3.18 on Intel Core i7 8th Gen., Nvidia GTX, X11 which are the latest versions from the openSuse repos.
All machines run openSuse 15.2 so there is no "\" involved as far as I know.