score:4
It's not unheard of but I don't think United has them. For example, Emirates does on their 'new generation in-flight entertainment system product':
Other new features on ice includes enhanced handset controllers, USB ports and PC power outlets on all seats across the three cabin classes to allow passengers to charge their own mobile phones and portable devices.
[...]
All PC power outlets equipped with HDMI & USB ports for charging of portable devices
Upvote:2
No. I've never seen an HDMI port on an airplane, and this one is no exception. It has USB ports in all classes, but no HDMI ports.