There is! https://radicle.dev :)
the fact that you, as the creator of a "competitor", post this as-is without a "At $co, we…" run-on is a good look
There is also ForgeFed/vervis
Oh, that's pretty cool! Now I can't decide whether that approach or one based on AT is better...
From today:
HardenedBSD Is Now Officially on Radicle
https://news.ycombinator.com/item?id=47944864