Authenticate user without credentials

Is there a way to authenticate user automatically based on IP of the user. The user will be only one but he/she can login to multiple devices directly without the login screen if the said user is from certain ip

You would need to implement a custom Authenticator in order to do that. See the Server Developer Guide section on Authentication for more information:
https://www.keycloak.org/docs/latest/server_development/index.html#_auth_spi