>3. Park a small reasonably low-power computer at a friend's house across town or somewhere a little further out -- it can be single-disk or raidz1. Send ZFS snapshots to it using Tailscale or whatever. (And scrub that regularly, too.)
Unless you're storing terabyte levels of data, surely it's more straightforward and more reliable to store on backblaze or aws glacier? The only advantage of the DIY solution is if you value your time at zero and/or want to "homelab".
A chief advantage of storing backup data across town is that a person can just head over and get it (or ideally, a copy of it) in the unlikely event that it becomes necessary to recover from a local disaster that wasn't handled by raidz and local snapshots.
The time required to set this stuff up is...not very big.
Things like ZFS and Tailscale may sound daunting, but they're very light processes on even the most garbage-tier levels of vaguely-modern PC hardware and are simple to get working.
I'd much rather just have a backblaze solution and maybe redundant local backups with Time Machine or your local backup of choice (which work fine for terabytes at this point). Maybe create a clone data drive and drop it off with a friend every now and then which should capture most important archive stuff.
Unless you're storing terabyte levels of data, surely it's more straightforward and more reliable to store on backblaze or aws glacier? The only advantage of the DIY solution is if you value your time at zero and/or want to "homelab".