Maybe OP means the collaboration feature. I don't know whether local typst supports that though. Expecting online collaboration in "local first" may be an oxymoron in itself...
The pro version of Overleaf supports offline work with a simple trick: every Overleaf document can be accessed as a git repo. It's a bit limited (there's no branches or tags, and it breaks the "track changes" feature) and trying to convince the average researcher to learn git is a challenge, but if you know git it works quite well.
There's also the fact that you can't auth using pub keys, and are consequently stuck using password auth (as a workaround, I usually just set the credential cache expiration to some huge value). Despite this, it's only half-annoying, but again, as you pointed out, only if one of your collaborators happens to have the premium version.
