I find in constraining to use only laptop hard drives or SSDs in this system as the cost is higher and the capacity is less. I wanted to try if this would accept desktop hard drives.

I bought a SATA data + power cable extension cable online in order to extend the connector outwards (so the 3.5in drive would fit.)

It worked! I was able to plug in a desktop hard drive to a thin client. You may need to trip the plastic on the connector to make it thinner so that it can fit.

I have also tried to put in 2 desktop HDDs at the same time and it worked. I had this 2 desktop HDD setup for a year as a low power server and it was fine.