The whole linking to other instances and services like lemsha.re or lemmyverse.link within Lemmy should become obsolete in the next release of Lemmy. It will include rewriting remote instance URLs to the local instance equivalent.
We certainly are nearing the first stable release, but there are still 14 open issues and more to come. Iirc one of the lemmy devs said that it will take a few months before we get stable 1.0.0. That recent release is probably some alpha or beta release.
Proof of process (e.g. a recording of you making the content) is the most reliable way. Big tech is also trying to push C2PA to mark AI made content, though that most likely will never succeed at what it is trying to accomplish.
I never really tried using Sync as I don't use proprietary clients. Summit recently got open source, it is pretty good and the dev is pretty fast at developing the app. Currently my main.
This is kind of like blaming the founder of knives because criminals use them to murder people.
It's dumb.