Currently I use a Mac mini as a home server. Photos.app on it is configured to download full resolution originals from iCloud, which then gets copied by a script to a backup directory on a third party server. Why the backup? Too many horror stories of libraries disappearing, risk mitigation, protect against me being stupid, etc.
I am getting rid of the Mac mini. I'm replacing it with a Raspberry Pi. Capacity wise more than sufficient for what I have the mini doing. Which is very little. I have a MacBook Pro, but the library is too big to fit on there.
Looking for suggestions on how to back up my iCloud Photo Library when the only full copy of the library is on the iCloud servers.