Hi @YISUUS

From the page you’re linking to it says
The username authentication method uses the system password file to verify a username and password combination supplied by a user as part of the SOCKS version 5 authentication process. Note that the password is transmitted in cleartext with this authentication method.

So that would probably mean that you need to create a user on Ubuntu and use that user.

But you would probably get better help by asking their community mailing list:
https://www.inet.no/dante/lists.html