You can try updating the BIOS to the latest BIOS version, please follow the BIOS update instructions here:
Please be aware that if the unit came with Windows 10 and you install Ubuntu this has not been validated and any error can be expected.
There is a version that comes with Ubuntu 14.04 LTS* (64-bit) already installed you can see it at the link I provided above.
As I explained, I followed the directions in the linked thread to make the stick run headless. This includes a BIOS upgrade (see comments 20 and 21). The BIOS upgrade did allow me to boot the stick headless, but it didn't make the power button work. As far as Linux's ACPI system is concerned, systemd-logind isn't getting any signals from the power button at all.
The version that comes with Ubuntu preinstalled is not an option as I need the extra RAM and storage for my application.
Is the hardware on the Ubuntu version any different from the Windows version other than the RAM and eMMC size? If not, you really should just post the Ubuntu build you'll support. Or just offer the better hardware with Ubuntu.
I would recommend that you check on the following post:Linux Intel Compute Stick running "Headless" hangs on boot with no HDMI monitor connected - suggestions?
Information about validated Operating Systems for Intel Compute Stick would be here: Supported Operating Systems for Boards and Kits
Ubuntu requirements do not need more than the hardware provided, also there is price difference.
I have the system booting headless with no problem after following the directions in the thread I linked to. I only mention it because there is no user interface in my application and I would like the button to work. Linking to another resource to solve a problem I've already solved is not helpful if it doesn't address the problem I'm actually asking about (making the power button work). If it's not about making the OS see power button presses and acting accordingly, it is not relevant.
Furthermore, I am aware that Ubuntu has more modest requirements than Windows. My application RUNNING on Ubuntu needs the extra RAM and storage. I am aware of the price difference.