for nextcloud i would need to set up a server that probably also needs to be always online. syncthing allows me to backup to my laptop and is opportunistic about it, ie whenever both are on wifi.

i am also using syncthing to manage my audio files. on the laptop i decide what i want to listen to by copying the files into a specific folder, and that gets copied to the phone. when i am done with a file i delete it from the phone, and that gets synced back to the laptop. syncthing is perfect here, and so using it for backup in the other cases is worth it over having yet another solution.