I’d use Dropbox to sync to a local folder or removable drive (not sure if this is possible as I don’t use Dropbox nowadays*), and copy (or unmount the drive) once syncing is complete.
*I still have a free account that is used for a few Roon backups, but this is an insurance policy. I copy to my network (backups locally and to cloud) and an attached USB drive.
thats what I’m currently doing with my Mac, but I’d like to lose the drive once I get the Nucleus. Just a minimalism thing, I reckon. It had never occurred to me that I could let dropbox handle the backup but then manually restore, as @mjw stated earlier.
I have my Nucleus in our main bedroom in a cabinet below the TV. I have a 1TB HDD that stays connected and backs up every night at 3am. Never a problem. The internal SSD is for music, but I have almost nothing on it (42 tracks).
I’ve had a Samsung T5 SSD for backups on a NUC/ROCK for over 3 years now. With the newer T7 in use on other systems. No issues with any of them. The T7 1TB is listed on Amazon for $104.00