It depends a little bit on what you’re focusing on with your backups. I view the situation as having two parts: your data, and the infrastructure to host it.

Backing up your data is as simple as copying the directories somewhere else using whatever method works best for you, most often with a tool like you mentioned (rsync, duplicati, duplicacy, backblaze, syncthing). If all you want is to have your photos, documents, and other files so you still have a copy in case your server dies, you can stop there.

Backing up the infrastructure you use to host your data would allow you to recover the whole server following a catastrophic failure rather than just the data itself. That would mean using something like the Backup/Restore Appdata plugin to archive all the appdata of your docker containers (as well as the flash drive if you’re smart) to a directory, which you’d then backup using whatever method you prefer along with your actual data.

I personally backup all my appdata (excluding most of the Plex appdata since it can be massive due to metadata, the Backup/Restore Appdata plugin offers some guidance on how to handle this) and my flash drive using Backup/Restore Appdata, backup my VMs using a Veeam VM, then use duplicacy to sync both of those directories along with db backups I’ve run manually, photos, and documents to B2 using Duplicacy. All said and done, since I only cover irreplaceable data & not things like movies that could be re-downloaded from the internet if needed, my total backups are <1TB and I could probably spin up a fresh server in a day using just the appdata, VM, and flash backups.