I think it's a hardware thing. From what I have read, the PC HDMI adaptor is wired specifically and will only work on the Gemini or Cosmo. Conversely, any other USB-C-HDMI adaptor doesn't seem to work. The only reason the DisplyLink adaptors work is because they actually have a small graphics chip inside them - so they don't rely on the host computer to send a display signal (AFAIK).