I have successfully loaded the HP Stream Mini with Ubuntu 15.04. Ubuntu wise, the system works as I expected.
The BIOS s UEFI loader and Windows boot manager certainly made the system very difficult to boot OS other than Windows. I wound up turning off the UEFI loader and wiping out the factory pre-loaded Windows 8.1. Is this how Microsoft locking out the other OSes to protect its turf?
The HP Stream Mini really makes an inexpensive but fine home theater PC. It runs 1080p real time streaming and playing back as smooth as silk.