Asus is currently inviting those who own the ROG Phone II to join its Android 10 beta program for this device. However, this only appears to apply to the ZS660KL model, the 12GB/512GB international variant. Those who wish to get this update need to join the OEM's mobile device forum, have an Asus Member's account and be prepared to submit a lot of sensitive info about the phone in question.
https://www.notebookcheck.net/Asus-opens-a-beta-program-for-Android-10-on-the-12GB-ROG-Phone-II.442586.0.html