On the Ruby, Majestic, Discovery and the Crown, there is a little toggle button on the bottom center of the tv. Turn the tv on and go to bridge cam. Pressing this button/switch/toggle will activate a menu. One of the menus is for input, there you can select hdmi 1. Bridge cam will now show what is being played on hdmi1.
Granted, getting to the sid of the tv for putting the firestick into hdmi1 can sometimes be difficult. But with patience, it can be done.
There is a complete step by step on youtube as well as on a forum here on CC dating back around the beginning of the year. I know the search function doesn't always perform well though. Good luck!!
Here is a guy on the Royal