Re: If you cannot touch it do not complain when it evaporates
if you read El Reg then you should be able to work this out for yourself. Just to kick off an idea:
Raspberry Pi 2B or later with Ubuntu for you plus friend with Bacula configured to either
a) Backup locally (with encryption) and then sync the backup files to friend via rsync, syncthing etc
b) Backup (with encryption) direct to friends Bacula Pi.
Friend does likewise to back to you. Encryption means friend doesn't need to be trusted not to look at your stuff.
Yes, you'll need enough disk at each end for each others data (or both if you use the first approach), but disks are cheap and for a domestic setup how many people genuinely need a working backup set of more than a few hundred GB of stuff? When you get more then 5 GB of anything you want to keep forever such as photos etc, burn to a DVD. 2 copies of course.
I have one half of the above setup to back up data to a pair of 1TB USB disks - full data once a week, incremental data every night, OS backups every so often. 1 disk is in the house being used, other in the garage just in case something bad happens in the house. Swap over once a week. Only had to do a restore once so far, and for that my most important user was extremely grateful....
There's gotta be many other ways you can do this. And not a cloud in sight.