Chromecast (2nd gen) and Audio cannot Cast in 'Untrusted' outage

I know they're on borrowed time (I've already lost one) but.. random data point, my Gen 1 videos are fine (just tested).

Which isn't the sort of thing that helps you or anyone else trying to debug this (but this article makes it sound like an age thing.. which.. seems unlikely if even older harder is happily streaming).