You might already know this, but in case anyone doesn't, but ERSC's CTO is the creator of jj.

Just to be clear about it, what we're doing is not a forge like GitHub, that is, a large single public platform for social coding. What we are doing is providing reliable infrastructure for the enterprise, initially as a BYOC on-premises option, and possibly a single-tennant SaaS. Keep your eyes peeled and/or use that contact form to hear about it when we're ready, we've been talking with some people for a bit but are going to be opening up more soon.

Tangled is doing the social coding thing, and they're jj-native as well. Been a big fan of their work for a while now.