I use NixOS so all my system configuration is already saved in my NixOS configs, which I save on GitHub. For dotfiles that aren't managed by NixOS I use syncthing to sync them between my devices, but no real backup cause I can just remake them if I need to, and things like my Neovim and VSCode configs are managed by my NixOS configs so they're backed up as well.

I'm currently using TimeShift to backup my desktop onto an external hard drive (the why is because of how simple it is to use) and I'll be making a copy of anything I upload to my jellyfin server onto the external hard drive as well. I hope to eventually have a dedicated backup server and have a duplicate of it at a friend's house for offside backup too

Multiple. Locally I have Timeshift doing btrfs snapshots every so often. This is mostly to roll back to a snapshot if something breaks. I've never had to use it (and probably should).

I use Pika backup every once in a while for a local backup to an external drive. Mostly because it's easy to restore quickly.

I have duplicacy doing backups to a cloud provider. I used to use duplicati for this, and it was fine - although I didn't like that it seems to be forever in beta. I like that duplicacy can do deduplication between backups of different machines which most other solutions I've seen cannot. I like its selection of cloud providers vs Borg/Vorta and some others.

I like pikabackup it’s based on borg