This is a Raspberry pi 3 b+ running Ubuntu 20.04 LTS 32bit (I downloaded from here) and the screen says:
Ubuntu 20.04 ubuntu tty1
ubuntu login:
And I cant fine the username password. Also I am new to my Raspberry pi and linex.
Username and password are both "ubuntu" according to this: https://ubuntu.com/tutorials/how-to-install-ubuntu-on-your-raspberry-pi#4-boot-ubuntu-server
Also, it on a PI 4 using Ubuntu Server 20.04, even though it presents the login prompt you have to wait about 2 mins for the SSH authorisation to be completed.
And when you login it does a load of unattended updates as of writing it installed 26 packages and you cannot install anything else while it does these update