@daviddelos, I set up a similar test workflow and the List Remote Files is working for me (after playing with the scopes and permissions a bit.
In my set up, I added the following scopes Google Authentication (API Key) node:
For the service account I set up to test this, I gave it the Storage Admin role in the GCP console. I did not experiment with assigning a less privileged role to the service account, but you could start there and reduce the privilege until it’s sufficient to your use-case.
-Jason