> Once you have it on disk, how do you get it away from your phone?

plug your phone into a computer? Install Termux and use one of the countless command line programs designed to transfer bits over a network?

I think GP was talking about how to transfer the backup 1) daily, 2) in an automated manner, and 3) reliably and in time (before, 48h later, Signal overrides the existing backup on your phone later with a new one).

This is not trivial when each backup archive is in the order of 20 GB.