It's only required for applications that exclusively use third-party auth, and this rule is only being enforced for new applications at the moment. After April 2020, existing applications will also have to follow this rule.

Trulia’s app has. I’m trying to think of others but I haven’t seen many yet.

I think I heard it’s only a requirement for apps that offer alternative social logins? And I’m guessing developers have a bit before that takes effect?

Existing apps have until April to implement it (after which they won't accept new versions of an app without it) and this developer season has been particularly busy so I expect many developers will wait until April.

Groupme: https://web.groupme.com/signin

I think Kayak was one of the first few to implement this since it was there the day iOS 13 rolled out.

I used it for the first time with TikTok just a few days ago.

in native IOS i've seen Mapster & TikTok

Glitch.com has it.

Zillow.