For people slightly less crazy than I am, it’s nice to hear B2 and Wasabi prices are at decent levels. But for me it’s more about paranoia and not trusting “them” or “the cloud” to care about my data as much as I do.
Plus, this is all for personal use so unfortunately “the billing stops here”.
Himachi is pretty limited these days since it was taken over by logmein. Neorouter is a good current alternative that provides similar functionality - there is a free version.
Simplest, lowest cost, peer-to-peer WAN backup approach by far:
Sign up for a free ZeroTier account.
Download it for yourself and your dad’s computer
Login to ZeroTier and create a network (just a couple of clicks)
Use the random Network ID it creates to add your computer and dads to the ZeroTier network you just created.
This will basically create a second, virtual, Ethernet interface on your computers and link them together as if they are on the same LAN and in the same IP subnet. The great thing about this is you do not have to deal with punching holes in firewalls and setting up port forwarding - no need to touch your home networks at all.
Install free Filezilla Server on both you and your dads computers. Install it as a service, so it will always be running in the background.
Install Duplicati on both you and your dads computers. Use the wizard to create a super simple FTP backup to each other’s computers. You will want to use the IP addresses that the ZeroTier creates (probably something like 10.12.12.13) as the FTP destination. Since the ZeroTier virtual network is encrypted, no need to deal with the hassle of anything more secure.
Set up Duplicati to try to backup fairly frequently (like each hour), and whenever you and your dad are online at the same time backups to each other will kick off. These backups will be super quick, since they are incremental in Duplicati.