Local express over localhost or a proper domain?
In the rig or the twitch website?
There can be a difference to the rules applied to localhost and real website and rig and real Twitch, due to how browsers and the rig works work, which is why hosted test exists in order to check things work how they should/apply the full CSP properly
But anywho, the Twitch player retains it’s access to the normal shortcuts, including double click to full screen. As then prevents user confusion at the double click not working, on some streams compared to others