With the trials of Crowd Play ongoing at the moment there are a number of people who are looking to use the feature but play from the TV. There isn’t a straight forward way of doing this at this moment in time. However this is a workaround to this if you are wanting to do this. I would like to thank LordVivec on Twitter for the heads up on this.
In order to get to play to CCU you will need to wait till you are selecting for Crowd Play. After the game starts to load wait and gets pass the Crowd Play things wait till you are at a safe spot i.e. character select for Mortal Kombat 11 screen. When you get to the safe spot you can then load the game up on you Chromecast Ultra and play it there.
While this is not an ideal solution is a workaround for the time being. I expect that you will be able join Crowd Play in the Chromecast Ultra at a later date and possibility by an Arena like system where you can see all the people streaming and you can view and join the queue there.