[steveklabnik]

Elsewhere in the thread it's stated that Tree Style Tabs has shipped a 57-compatible version, and that LastPass will be ready by the time this all hits stable.

[mdek]

True. I did in fact have to explicitly downgrade TST to the <57-compatible version. The new version apparently doesn't yet support hiding the tab bar across the top of the browser.

[floatboth]

I think the API for hiding the tab bar hasn't landed yet. You can do that with userChrome.css for now.