I leverage btrfs or ZFS snapshots. I take rolling system level snapshots on a schedule (daily, weekly, monthly and separately before any package upgrades or installs) and user data snapshots every couple of hours. Then I use btrbk to sync those snapshots to an external drive at least once a week. When I have all of my networking gear and home services setup I also sync all of this to storage on my NAS. Any hosts on the network keep rolling snapshots stored on the NAS as well.

Important data also gets shoveled into a B2 bucket and/or Google drive if I need to be able to access it from a phone.

I keep snapshots small by splitting data up into well defined subvolumes, anything that can be reacquired from the cloud (downloads, package caches, steam libraries, movies, music, etc) isn’t included in the backup strategy. If I download something and it’s hard to find or important I move it out of downloads and into a location that is covered by my backups.