If it fits your use case a separate user account (on the operating system) or a whole disk partition with VeraCrypt could be used to safeguard a proper desktop installation from unauthorised access. Joplin Portable is a fine piece of software, but it takes a very long time to start.

And it has no access to the OS's key chain to store your E2EE password which means that it's stored in plain text in your Joplin database. Maybe that doesn't really matter as in your scenario local storage is encrypted anyway.