https://twitter.com/Microsoft/status/1387421368581455874 These are the five candidates that it seems like the font was picked from, of which Bierstadt appears to have been chosed and renamed to Aptos. On the surface the new default font looks a little like Public Sans to me.

Tenorite seems to look like some form of a Gotham ish one, Grandview is some form of DIN it seems.

Here's an example of the five fonts, Bierstadt, Skeena, Seaford, Grandview, and Tenorite. https://imgur.io/gallery/Dx91rtr