I can confirm this bug on a System76 Kudu Professional (i7-4900MQ).
Booting with 3.19.0-18-generic, I don't get any HDMI option in the Output tab in the sound settings UI.
Booting with 3.19.0-16-generic, I get an HDMI option and it works fine. So this is definitely a regression between 3.19.0-16-generic and 3.19.0-18-generic.
I can confirm this bug on a System76 Kudu Professional (i7-4900MQ).
Booting with 3.19.0-18-generic, I don't get any HDMI option in the Output tab in the sound settings UI.
Booting with 3.19.0-16-generic, I get an HDMI option and it works fine. So this is definitely a regression between 3.19.0-16-generic and 3.19.0-18-generic.