Lots of people have mentioned rsynx, restic, borgbackup, and others, but which would be best for backing up nextcloud, immich, and radicale? Do all of them have a method of automatically backing up every X days/weeks? Why use one over the other, what are the differences?
Haven’t used all of those but my recommendation would be to just start trying them. Start small, get a feel for it and expand usage or try a different backup solution. You should be able to do automatic backups for any of them either directly or setting up your own timer/cron jobs (which is how i do it with rsync).
And trying restore a lot, don’t be like me!