I use:

• 3-way zfs mirror for important data like photos, documents
• snapraid for bulky and less important data like movies
• hourly backup of important data and a subset of the less important data (difficult to find movies) to a rpi with a big disk
• daily backup of the same data to a friend. We have a system where we put a hdd in each other’s server and have ssh access

Backups are done using restic

Off-site rather than offline, protecting against things like your house burning down.