Yep, I use rsync to sync files / directories between my desktop, laptop and even phone (Android). Also an external drive.

I ended up creating https://github.com/nickjj/bmsu which calls rsync under the hood but helps you build up a valid rsync command with no surprises. It also codifies each of your backup / restore strategies so you're not having to run massively long rsync commands each time. It's 1 shell script with no dependencies except rsync.

Nothing leaves my local network since it's all local file transfers.

Until I want to share with say… anyone that isn’t on HN :)

Except that for macOS it uses the FileProvider Framework. So files that are rarely accessed get deleted from your local storage and synced back automagically when you access them. Saving space on your disk because on mac you can’t upgrade your ssd without a soldering iron.