Farming on a Rock Pi 4A

Has anyone tried farming on a rock pi 4a?
Are you using the GUI?
How many hard drives are you adding or can you add? I installed ubuntu mate GUI and it works but I am running into a warning that there is not enough Disk space. However, there is plenty of memory but I don’t know why the error is coming up?

any suggestions on how to get the most out of the rock pi?
I originally wanted to use the command line but I am a rookie and couldn’t get it going.

Greatly appreciate any advice or tips.