Is there, or will there be, a way to password-protect the UI running locally?

we do have that functionality when you leverage Prefect Cloud: app.prefect.cloud for OSS, check out https://discourse.prefect.io/t/why-does-prefect-2-0-doesnt-include-auth-and-rbac-features-as-part-of-the-open-source-package/741

Makes sense, thanks. Cloud it is.