Last time I tried Tangled they had no concept of private repos. That’s the only thing keeping me on GitHub (oh, and my massive likes collection, I use those as bookmarks).
I’m self-hosting with cgit, maybe I could move my private repos to SourceHut? Idk.
There's an AT protocol working group for private data: https://atproto.wiki/en/working-groups/private-data
But you're right, the protocol doesn't currently support this.