If you want to have a play with the app, both EK & EY have shared their invitation codes on the WWW for people to set it up. Once you're in, I'm quite sure it's airline agnostic (in fact - the code for EY & EK Android devices is the same). I've done it using the Emirates iOS code and added my [verified human] picture and AU ePassport (including RFID scan to validate the chip), but can't add my January QF INT flights or the AU international vaccination certificate, as yet. I suspect it's just too early for both of these to be there to add.
Etihad (EY) invitation code - Apple iOS: 123412
Etihad (EY) invitation code - Android: 787350
Emirates (EK) invitation code - Apple iOS: 250573
Emirates (EK) invitation code - Android: 787350
Here's a video on how to set it up:
https://inarilt.myds.me/Produccion/IATA/video/ITP/travel_passt_app_01_V7.mp4