Video plugin supports Channel 9 but Microsoft doesn't anymore.
https://en.wikipedia.org/wiki/Channel_9_(Microsoft)
Maybe things moved to Microsoft's Learn thing. It also seems that web archive has old content and someone on the internet has built an index
https://walkingcat.github.io/ch9-index/
And the Key from a TEDx Talk page shows something getting redirected and then a complaint from youtube about displaying content in a frame... must not be getting the embed code right anymore.
From Eric, via matrix