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.

I really hope the typst webapp gets git support soon so it at least gets feature parity with Overleaf in this department (issue tracker: https://github.com/typst/webapp-issues/issues/25).

As far as I know, local Typst does not support collaboration. At least not in the way the online version and Overleaf do.