VEB server was not listed in the proxy role section, so that leaves only the repository role. I made a CIFS share of the local shared folder C:/Backup on VEB server just for test and it is presented normally as a backup repository.
In the listing for replica metadata repository there was the VBR server as the only option - DD repositories are not listed !?
Now I can choose that new mapping as CIFS share and remove the VBR server from repository role...
Will do the report how it went next week, after the testing.