Welcome to the forum @lhs_azevedo
The use case and topic title are a bit hazy to me. Is the idea that users keep the files they want backed up on the server, and then a privileged Duplicati backs up all locally, or does Duplicati do backups over SMB?
Backups where SMB is the source is not preferred for numerous reasons, but people do try them anyway. Some of the same issues occur (but more severely) if this is getting into SMB read of the DB (more later).
Assuming it’s central backup of local files, then restore could be done to local files, but the issue would be to keep users out of each others’ files. If you give access to the Duplicati GUI, users get access to all of it.
You can run multiple Duplicati to limit such sharing to groups (or even individuals) but it doesn’t scale well. Having multiple backup jobs in a single Duplicati is a bit better (if nothing else, a breakage doesn’t lose all). You also have a way to control backup file access on a fine-grained basis using some sort of permissions.
Maybe the reference to “read-only database” is asking whether having SMB access to the Duplicati DB is enough to allow some sort of restore. If one had that plus access to the backup files themselves, one can theoretically put files back together for restore IF everything will stand still and be consistent while working.
Currently Duplicati is not designed for simultaneous operations, e.g. simultaneous backups, or file restore during backup. There are discussions on both somewhere, but I’m not sure if they’re feature requests yet. Regardless, I think careful orchestration is required. If the idea is separate access, that’s probably unsafe.
As a side note, be careful about putting databases on networks. They contain secrets, so need protection.
If users currently have access to their backups as raw files, they can do a direct restore to create a partial temporary database using their own Duplicati copy to restore to their own machine. It’s a single-use thing.
How to refresh revisions imported from file and restore from another machine? is a similar wish of setting up a long-term ability to restore elsewhere, easily, safely, and with the latest version of source files. Some other questions have spoken of “collaboration” which is even further from what Duplicati is designed to do.
Doing “direct restore” in the middle of a backup that’s changing the files is hazardous, but maybe could be helped by timing, e.g. make sure no backups run when the users are restoring, or snapshot files for them.
To continue, please clarify the feature you wish. If read-only database can’t do it, maybe another way can. Short-term, this will have to be based on creative use of what’s there. Eventually, maybe design changes.