It seems like the people who got it to work were using the old GeForce Experience app and had been letting it run in the background on their PCs.
I did not have GeForce Experience, instead I downloaded the Nvidia App, launched the game from the app, and played for 50+ minutes as directed on the promo page.
I did this multiple times and got nothing, not after the first session, not after waiting a while and restarting the app, not after doing several more sessions.
Gave up, uninstalled the app.