Restic, it has native S3 compatibility and when you combine with something like B2 it makes amazing offsite storage so you can enjoy the tried and true 3-2-1 backup strategy.

Also fedora magazine did a few posts on setting it up with systemd that makes it SUPER EASY to get going if you need a guide.

I have an ansible role that configures it on everyone’s laptops so that they have local, NAS, and remote, B2, backup locations.

Works like a charm for the past 8+ years.

Restic or Borg. For restic I use the great Backrest web GUI.

I mounted an USB drive to one of my OpenWRT access points and backup on that one.

Rclone or fuse can mount/access Google Drive and can be used as back end for your backup choice.

Simplest backup ever: restic/Borg on a folder on the same PC. Not very recommendable, but indeed a good starting point.

Zfs/brtfs seems a complex solution for a simple problem. True is that once you start eating you get hungrier so maybe worthwhile.

I use duplicacy, it's free as cli and pretty cheap if you want to manage the backup via gui. Restore by gui is always free and I would recommend it because it's way easier to navigate the backups if you want to restore single files or folders.

rclone & restic work okay together to create backups in a Google drive mount. There are "issues" with backing up to Google drive since it doesn't guarantee file names are unique which is... a choice... but it should be reliable enough.

There's different kinds of backups. For this you don't need off-site storage.

For this I set up zfs auto snapshotting which means when I delete stuff it isn't really deleted because a snapshot is still pointing at it until it rolls off the time window.

Both zfs and btrfs can do this but you do need to change the filesystem to use these which can be a lot of work.

Borg borg borg

You can combine it with a FUSE mount of the Google Drive, I’m not sure if that works but I don’t see why it wouldn’t.

simplest tool to backup to Google drive

Without the need for versioning, I think rclone fits the description. For backup into USB drive / remote SSH server I would recommend rsync.