Download and setup the Imager tool for writing Ubuntu to a micro SD card or USB: https://www.raspberrypi.org/software/
Select “CHOOSE OS”
Select “Other general purpose OS”
Select “Ubuntu”
Scroll down the list to find “Ubuntu Server 20.04.2 LTS (RPi 3/4/400) 64-bit
After clicking on this, select “CHOOSE STORAGE”
Select the disk to write to
Click on “WRITE”
When writing is complete, insert the micro SD card or USB into the Raspberry Pi and power it on.
If you have no screen connected to the Raspberry Pi, you need to find the IP address of the device in order to connect to it with SSH. For this you can use tools such as Angry IP scanner: https://angryip.org/
