Syncthing is a server. You're replacing the server part of Radicale with another server software, which comes with extra overhead and complexity.

You've made a sweeping generalization in implying that since 4chan "as a platform" has caused harm, then all of its users are guilty/complicit and must relinquish their right to privacy. That and you're still misunderstanding the meaning of "fundamental" in this case, since that adjective would suggest that the right in question is not counted among those that would be taken away from you in case of moral/legal transgressions.

Isn't that just overcomplicating things for no reason? Radicale provides WebDAV endpoints that clients (including DAVx5 on Android) can just connect to, to synchronize calendars and contacts. All of this setup seems to just do all the sync part manually through Syncthing rather than just use Radicale's built-in functionality.

So privacy is a "fundamental" right, except if /u/[email protected] thinks you're a distasteful individual.