After reading that thread I mentioned above and this one it sounds like one strategy is to backup the full system while excluding all the directories that are not necessary for a replication or that will cause issues, but I honestly do not know enough about Linux to confidently identify each one.
I then realized there are certain actions required when restoring that I am unfamiliar with. In the first thread the OP describes mounting a hard disk, restic restoring to it, and running chroot then getting it ready to boot from… but I believe I am booting from the only volume mounted on this server.
I guess my question there is; what is the technique for a full system backup while on the same volume?
I am also treating this as a bit of a research project so feel free to be a bit brief and just send me materials! I can ask questions later 