Those mostly seem to be basically naked pc:s with a completely perforated case and lots of fans. This would make them very vulnerable to dust.

I was thinking of the opposite: the case being the heat sink. The Fanlesstech blog presents these sometimes. https://www.fanlesstech.com/

I don't know if it's enough to just cool the CPU (and using integrated graphics) and let convection handle the other components? Does the chipset or memory need active airflow over them?