Yes, you need a microSD card. The AML-S905X-CC-2GB is just a small computer. The microSD card would be the “Hard Drive” of the computer and is very necessary.
The other option would be an EMMC module as mentioned in the post shared above.
You generally will need to pre-load that microSD card with an “image” or copy of linux or another operating system that is compatible with the board, using another computer to load it on.
Libre Computer has a number of pre-built compatible images that can be loaded, along with a few tutorials on how to load them. The main images available at the link above are Ubuntu and Raspian. Ubuntu is probably the most “User Friendly” version of linux out there, but will be a bit of a resource hog than Raspian would be (at least in my opinion)
I intended to make a longer post with instructions/walk through links for writing images to cards. Then I got distracted and its been 2 days. So I’m just posting this as is.
I have installed Raspian to the microSD card (unconnected to my network) and it brought up the desktop. I did not do any updates since I was not connected to the network. Once connected via ethernet, I cannot SSH into the Le Potato. I can ping it from Windows but trying to get to it via Putty fails every time. I get "Network Error. Connection refused.
Red and Green lights are on solid and the Blue light blinks quickly continuously.
I’ve built Raspian on 3 different microSD cards with the same effect. My USB puts out 2.1 amps so I believe I am OK there but could use some guidance.