How can I unlock all menu items in the Team menu?

A lot of these are Cloud features so they are not available on Server. Prefect Cloud has a generous free tier of 20k task runs per month, which is way more than enough to get started with

@Kevin Kho I see, Can I still use secrets on Server by adding it to configs.toml file?

Yes you would have to use local secrets. It’s because there is actually a Vault service in Cloud that is not in the open source version