you do not need Chromecast… The App AirScreen on Nebula provides the Casting feature to Nebula, so that you can “cast” media to it, similar to how you would cast to an actual Chromecast device.
This is how I am using Disney+ today on Nebula Capsule
Steps to Chromecast Disney+ (Plus) using Chrome Browser.
#1 : Open the Chrome browser and visit disneyplus.com .
#2 : Tap the LOG IN button located at the top right corner of the screen.
#3 : Enter your Login credentials.
#4 : Select and stream the Disney+ content that you want to cast.
#5 : Click the Cast icon located at the top right corner of the media player.
#6 : Choose Nebula AirScreen (or whatever name it shows you)
Or you can simply use iPhone or Android device to cast!!!