you can easily backup the server where you have your bareos installation with the 'self'-Backup.
I have found the relevant settings to enable the register-card for bareos-backups on UCS under:
Domain - LDAP: univention / custom attributes / bareos. In the module-tab you can add other domain-roles for backup.
I have done this some time ago but remember that the apparently blank first and third field - are just appearing blank! That's kind of strange, but I think what you don't see is the Linux and Ubuntu -role. But they are nevertheless enabled through these fields. So start at the end of the list by adding/ choosing new roles.
I have never tried to regain access or to rebuild a UCS-Server with the backups I've made. I just think there might be some reason why it is not enabled by default. But Member and Slave should be fine in most scenarios?
I also did mark this as dangerous - It was written out of my memory and when I tried it out now... there is still an issue (?) with choosing 'Computer: Linux' and 'Computer: Ubuntu' here. Meaning, that you can't chose them and they are gone if you add another item. I will write this as a question - but another time. (Last time I did manage somehow to get Linux and Ubuntu back, but I've forgotten how...)