https://news.ycombinator.com/item?id=44124688

So the source is a twitter meme?

Featuring a screencap of an MS engineer's talk from some React conference, yes.

The talk in question showcases a widget in the start menu that's using react native. Apart from the meme itself, I have not found indication of the start menu being a react native app. Every time this comes up it seems to always lead back to that meme.

That'd be correct. See also the top comment in that thread that (evidently after I originally read that thread) also explained exactly this, and a sibling comment in this thread tree that also did so (more than two hours after I posted my original comment, meaning I was unable to amend or delete it).

the talk is linked as well: https://news.ycombinator.com/item?id=44125217