iPhone backups to external disc ONLY

I know this question has been asked before and a solution posted but that solution no longer works.

Earlier this year you could paste a little command into Terminal (found on Lifewire) to tell your iOS devices to backup to a folder (ios_backup) on an external drive rather than your Mac's HD.

This is quite important and a real concern particularly if, like me, you have a 1TB capacity iPhone and an iPad and a partners iPhone that require backing up but don't really want to fill up the 1TB drive on the MacBook Pro alongside all the applications that reside on the drive. Available disc space is therefore precious.

So why isn't there an option under 'Backups' in the iPhone devices window to say "Back up all the data on your iPhone to an external drive"?

Currently under MacOS Ventura 13.2.1 the Mac always creates a backup folder in the MobileSync folder under Application Support on the HD and no amount of tinkering seems to change that behaviour.

I think the answer is probably that Apple has designed it that way to keep the system robust and predictable... unless of course you know of another solution.