Just in case anyone stumbles on this post as I did:
I bought a new Pixel 9, which was delivered, updated and fitted with Graphene OS a few days ago (1 december).
I was unable to find the Rabobank app in the Google Play Store, as it is officially incompatible. However, I was able to download and install from Aurora without a hitch. I activated using the Rabo scanner and that worked perfectly.
At the time of writing, the app appears fully functional.
I did not attempt activation with an ID card, so I can't say anything about if that works.