When Tony goes camping with his RV, he'd like to broadcast YouTube TV from his phone to his TV. Leo says that in theory, Chromecast will work because he's connected via WiFi. However, it requires being on the same WiFi network, so if the phone is using WiFi, it can't really do that because he will need internet for the Chromecast. Getting a "MyFi" router may be the solution, but it would have a separate cellular connection. But the good news is, it also has its own bandwidth data allotment. Get a MyFi from your carrier, then the phone can join that, and the Chromecast can be on it. Another option is to use the TV's SmartTV connection and use the phone as a hotspot. But a SmartTV needs to support YouTube TV with an app, so check the TV app store for it.
Doctor Mom in the chatroom says he can connect the smartphone directly via USB-C and an HDMI adapter. The chatroom says he can also use a WiFi Extender and use his phone in Hotspot mode.