I use kup to back up my important PC files (the basic pre-installed backup software on KDE neon), which backs up to a separate drive on my PC, and that gets synced to my Nextcloud instance on my local server, and that - along with all the other data for my containers running on it - gets backed up by Kopia to DigitalOcean spaces.
I couldn't recommend Kopia strongly enough, because you have such fine control of what gets backed up, when it gets backed up, how many to keep etc. and it is versioned so doesn't grow exponentially, and it compresses and encrypts the backup. I also have a setup where it executes a script before and after the backup starts that stops and starts the containers to maintain file integrity since nothing will be writing to the files. And it's also a Docker container so it can just fit into your current compose setup.