We have several communication channels that we actively support, each for different purposes.
Filing Bugs and Feature Requests
If you have identified a bug in Cobalt common code - meaning that you don't expect that it is related to a platform or port implementation quirk, then you should file a bug on our public issue tracker.
Additionally, if you have specific feature requests, you can also file them on our public tracker, but they should be very concrete and well-specified. If unsure, ask about your request on cobalt-dev first.
You will need a valid Google account to post. You can create a Google account with a non-gmail address (say, your work email address).
Asking Techincal Questions
For programming related technical questions about Starboard or Cobalt, we encourage you to search through and post questions on Stack Overflow (SO). The team actively monitors for Cobalt-tagged questions on SO.
Stack Overflow has guidelines about what kinds of questions are acceptable. In particular, they should be about some aspect of coding, and not questions about schedules, future plans, certifications and so on. Additionally, they should not be bug reports or feature requests, those should be filed on our public Issue Tracker.
Asking about Schedules, Discussing Features, Announcements, and Miscellany
We also have a dedicated mailing list, firstname.lastname@example.org. If you are spending time with Cobalt, you may want to subscribe. And if you have a concern that doesn't fit into the above categories, asking about it on cobalt-dev is a reasonable course of action.
If you are using Cobalt for YouTube on your device, and have YouTube-specific questions, you should contact your YouTube technical account manager directly. The above forums are Cobalt-specific, but not YouTube-specific. The Cobalt engineering team can't speak on behalf of Google or YouTube.