Syncthing + NextCloud + rsnapshot backups would have been my open-source alternative recommendation, but of course not everyone wants to take the time to learn that skillet, set that up, and maintain it.
You can get the whole package from Hetzner pre-configured, or just configure it yourself. I manage our team's nextcloud installation, and installing on bare-metal (sans containers) is a half day job at most.
Moreover Nextcloud supports WebDav which allows tools like Zotero to directly tap into that.
Would you say that the install and maintenance load for both systems (Dropbox vs packages containers) is the same?
Like, I'm confident my tech illiterate parents could get drop box running. Ease of use and UX are features.
I'm not saying the self hosted stack is bad, and in fact it's probably better in many ways. But it doesn't have the same feature set if you consider usability a feature, imo.
What does Syncthing add to the Nextcloud capabilities? (Honest question because I'm curious; I have a NextCloud & snapshot to encrypted S3 backup solution already.)
I admit I have not used NextCloud, but the hands-off automatic file-sync-between-devices that Syncthing provides has been transparent and seamless. It has required no babysitting after initial set up.
I have forgotten if NextCloud does this, because I don't use NextCloud at this time, nor have I.
Or are you saying, "well, with a completely different stack I can get closer to feature parity"?