I have a related problem. My Core is a SonicOrbiter, and thus far, my Roon backups have been on DB. Like the others here, I too want to move my backups to iCloud, as I see no purpose in paying DB any longer.
I followed all the steps you mentioned here.
On my Mac, I did the following:
Roon – Settings — Backups
Add Network Share.
Copy pasted the smb network share location.
I got the following error message: There was an unexpected error: Invalid Network Path. I then pasted the IP address of my Mac. No dice.
I’d appreciate some help sorting this out please.