I'd like to manage resources across >1 Azure subscriptions simultaneously in one Pulumi program / stack. Is there a good example for this scenario I could start from?

You can create multiple providers Not sure if there is an example using azure, but essentially you pass the provider to the resource options

Thanks! Is there any other (non-Azure) example I can get insights from?

Perfect, thanks! That's exactly what I was looking for!

Explicit providers is the way to do this as @little-cartoon-10569 suggested. Here's a Go/AWS example that iterates a list of regions to deploy to and creates a provider and set of resources in each region - https://github.com/pulumi/examples/blob/master/aws-go-console-slack-notification/main.go. The concept would be the same for Azure or any other provider.