I do an automated nightly backup via restic to Backblaze B2. Every month, I manually run a script to copy the latest backup from B2 to two local HDDs that I keep offline. Every half a year I recover the latest backup on my PC to make sure everything works in case I need it. For peace of mind, my automated backup includes a health check through healthchecks.io, so if anything goes wrong, I get a notification.
It's pretty low-maintenance and gives a high degree of resilience:
A ransomware attack won't affect my local HDDs, so at most I'll lose a month's worth of data.
A house fire or server failure won't affect B2, so at most I'll lose a day's worth of data.
restic has been very solid, includes encryption out of the box, and I like the simplicity of it. Easily automated with cron etc. Backblaze B2 is one of the cheapest cloud storage providers I could find, an alternative might be Wasabi if you have >1TB of data.
Also you know it's also possible to setup backups on the drive connect, also a good thing to turn off the networking beforehead 😶🌫️
(Also it's possible to do "timer usb hub", it's not very off-site, but a switch can turn on every X days and the machine will mount it and do the backup, then the usb hub turns off (imagine putting it in a fireproof safe with a small hole for a usb cable))
Also, i'm using ntfy.sh for notifications
And if you're using raid, you can setup it with on a drive failure