Thanks for taking the time to write in and share your report - it’s good to see you on the community again!
Since your Roon Server is running on a Nucleus, and you are using a Mac as your control device, you’ll need to setup a network share between the Nucleus and your Mac for backups to be saved on the Mac.
Here’s an article on how to do so:
Note that this article refers to adding a music folder, but you can follow the same steps to setup a backup location as well. You’ll access your Roon Settings>Backups instead of Audio.
Thank you, I think it worked. I had failed many times. I did reenable smb, and this time I entered the user and password, which I didn’t before, because it said when required.