

To be honest, they offer different use cases, so no, probably not.
Syncthing can be used collaboratively, inasmuch as I could share a folder with my wife, for example, but I think the primary use of it is to enable syncronisation of a folder between several personally accessed computers. If you do share with others, you’ll have to share a separate folder, so will end up with a bunch of different folders all being shared with different computers.
Not to mention that Nextcloud offers other functionality that isn’t necessarily possible with Syncthing. That said, I guess you could save your calendar to a folder in Syncthing and have it sync between devices. So I suppose it could replicate some of the functions.
Ah, that’ll be why it feels rock solid then…