(Replay engineer) Google is currently the only way unfortunately. We wanted to support secure logins at launch, with SSO and Multi-factor Authentication, and focus most of our efforts on the core product. As a result we just went with Google for launch.

We don't currently have any plans to add additional authentication mechanisms but we've heard this feedback from a couple folks and we'll sit down to prioritize it after the excitement of launch has died down. Sorry about that!