Hi, I'm trying to create a GitHub Action that deploys Pulumi but I'm running into the problem that my pulumi up command requires access to multiple aws accounts in order to run (one where the backend is stored, one where the DNS name is stored, and one where the actual deployments happen). I've tried to set up OIDC access to these accounts via IAM roles but I can only assume one role at a time. Any help or guidance would be much appreciated

You can configure aws providers to assume a role when executing. You can set up cross-account policies that allow your 'entry' account role to assume a role in each of your other accounts, and then associate providers with each of those roles. You then use those providers to provision your resources.