If the video does not display above, go directly to Facebook or Twitch. The Twitch stream works in mobile browsers.
Facebook Advantages: Chromecast support in desktop Chrome and mobile app. A lot of people use Facebook. Disadvantages: ~13+ seconds of latency. Viewing stream on mobile device requires app or desktop view in mobile browser.
Twitch Advantages: 3-7 seconds of latency with low latency mode. Stream viewable most in mobile browsers. Chromecast support in mobile and desktop Chrome and app too. Disadvantage: Quality may degrade in low latency mode.
Mixer Advantages: 2-3 seconds of latency with FTL mode.* Stream viewable in mobile browsers. Chromecast support in mobile app. Disadvantages: No Chromecast support in desktop Chrome, yet (just cast the tab and full screen the video). FTL mode requires app on mobile devices. See Really Live.
Smashcast Advantages: Not being tracked by Facebook, Amazon or Microsoft. Chromecast support. Disadvantage: ~10 seconds of latency.
*FTL currently disabled as of April 28th, 2019.