Instructions for anyone lazy:
• Drag down your quick settings and long-press the Smart View tile.
• Tap on the three-dot icon in the top right and open settings.
• At the bottom of the screen, open the about Smart View menu.
• Rapidly tap on the part of the screen that says Smart View 10 times.
• When prompted, enter the password: #00rtsp00
• When the developer options menu opens, enable the Google Cast toggle.
Same, one of my favourite games of all time!