Well, TestFlight states “The developer removed the build you were testing. Turn on notifications and we’ll notify you when a new build is added.”
The link to TestFlight for the AppleTV app from the forums might lead to a different build though since following it leads me to a “β is full” warning instead of just showing me the β I’m enrolled in already…
I still have the builds from before on my AppleTV though, but I suspect it might be wiser to simply remove it.
It’s a bit sad. Despite it’s issues, it was still working better than the official build (which, for some reason, no longer properly lists casts for movies and series and no longer shows what other movies they’ve been in).