Hello duc,
Thanks for your question.
No, it's not possible for an external user to log in without being invited first. This is a security feature to ensure only authorized users can access specific tenant data.
Alternatively, you can configure self-service sign up. https://learn.microsoft.com/en-us/entra/external-id/self-service-sign-up-overview
You can mark it 'Accept Answer' and 'Upvote' if this helped you
Regards,
Abiola