They don’t work in Chromium 90.0.4425.0 either on the same machine. My bet is that the server that hosts videos on their landing site might be misconfigured in some way.

It work on both my firefox and my chrome. The server that host the video is cloudflare. I will bet that you run a mac that doesn't support the encoding used. What I see is that the video is not served in multiples parts but in a single HTTP request.

On windows and Firefox, it fails with network error partway through buffering. Repeated refreshes make further progress, until I had the whole thing.