They definitely do run on Azure. Probably not 100%, but at least some footprint of those services do.

Are you absolutely sure?

They don't, however authentication for those services relies on Entra ID which seems to be affected.

I'd say DNS/Front Door (or some carrier interconnect) is the thing affected, since I can auth just fine in a few places. (I'm at MS, but not looped into anything operational these days, so I'm checking my personal subscription).