Hi, I don't know if this is common knowledge or not, but the xiaomi mibox is reely simple to take apart. And it has an antenna connection on the pcb but no attached antenna.
The "heatsink" is a metal plate mounted in the top "clamshell". I cut a hole in the top plastic and attached a stock Intel cooler (without fan) on the "back side" of the original cooler, now it runs a little bit better during heavy usage 👌
Pics or it didn't happen?