Apple TV support for Captive Portal WiFi authentication
Has an feature request been submitted to add support for Captive Portal WiFi authentication on ATV?
Apple TV 4K, tvOS 11
We can’t see which requests have been made, but it seems likely that you are not the first. More interest may help prioritize new features, though. Feedback - Apple TV - Apple
LAN networking features of the Apple TV wouldn’t apply to many captive portal networks. It wouldn’t surprise me if such access was purposefully omitted.
Alternatively, you may create your own small LAN in between the captive portal network and your personal devices, using a travel router, like a best of both worlds. If the network admin allows for that.