YouTube TV users can't sign in on Chromecast w/ Google TV - 9to5Google
Chromecast
Google will give you the new Chromecast for free if you pay for one month of YouTube TV - The Verge
New YouTube TV sign-ups offered a free Chromecast with Google TV - SlashGear
Chromecast And Google Home App: Sign of Things To Come
How to Set Up Your New Chromecast
Google Chromecast Review: Use this small HDMI dongle to get YouTube and other Google content onto the big screen - Home Entertainment - Media Streamers - PC World Australia