For your information, after using Tardigrade for a half year, I would like to revisit my post above.
Basically I have replaced Nextcloud with Syncthing.
Syncthing is a continuous file synchronization program. It synchronizes files between two or more computers in real time, safely protected from prying eyes. Your data is your data alone and you deserve to choose where it is stored, whether it is shared with some third party, and how it’s transmitted over the internet.
I noticed there was no need to run a VPS server to sync data among PC, laptop, and smartphone. You just have to install Syncthing to them, sync data among these peers, directly.
On Syncthing it is also possible to sync data with your friends by sharing a folder. Think of it as Dropbox / Nextcloud without a central server.
In order to back up data to Tardigrade, you can set tasks on Duplicati. Duplicati has a native implementation of Tardigrade. For more information, see: https://documentation.tardigrade.io/how-tos/backup-with-duplicati
Duplicati is a backup tool. It can group, dedupe, and compress small files into bigger blocks. It is a great tool for reducing the costs of cold storage. It also supports versioning.
You can set up Duplicati to run backup tasks hourly, daily, weekly, and so on. You may also run tasks minutely, but I am not quite sure if it supports to watch for changes to run tasks automatically.
On Duplicati, data is downloaded from Tardigrade to verify backup (and also when you restore a file, of course). Since data is synced among peers first, you can keep egress consumption minimized, and it should be much cheaper than syncing among Nextcloud clients via Tardigrade.
Also, this way every data is distributed. There is no central point of hacking. This is nice too, right?
Cheers,