Maintaining local, off-line backups is an endless PITA. But consider the alternative... :(
It's insane to me that there isn't a simple, GUI-based app that provides this utility in a clean, straightforward way. Basically just "dropbox, but let me set the destination to another drive on my PC/network/VPN (or a 'repo', for 'advanced' users)".
Just a plain interface that shows me my files and allows me to say "I want this folder to be backed up to here, here, and here". I can do that manually for every folder I want backed up, but other users may opt to backup a whole drive or whatever, depending on need.
Seems like a slam dunk. Frustrating that I don't know enough about the footguns with backups (duplications, cpu limiting, etc) to just write the app myself, but I have been looking at what the eframe and rustic libraries can do together. Feels imminently do-able by someone who has a lot of experience with backups. But maybe it's even passable do-able by someone who just knows what he wants.