I also had something happen with a well-known messaging app. They gave me a take-home assignment that turned out to be pretty non-trivial (16+ hours). They liked it, even had good things to say about it, I had an hour mostly non-technical meeting with a manager(?) there that seemed to go reasonably well, and nope, they weren't interested.

I told people to avoid this place because of how bad of an experience it was.