You can initiate casting before attending a meeting by selecting ‘This meeting cast’ option, or at any time during a meeting by clicking on the three-point overflow menu at the bottom right and clicking on the same option. Google notes that the feature works with the Chromecast Ultra, first and second gen Chromecast dongles, and Cast-enabled TVs as monitors, though performance may vary.
Meet on Chromecast shows users their other participants in a more life-size size while still using the camera, microphone and audio from their computer. It will roll out in the coming days both online and in the app. Make sure you are using the latest version of the Chrome browser and Meet app, and make sure your Cast devices are on the latest firmware.