I don't know if you know this but Pulumi has a
registry listing all available provider packages, but if someone hasn't listed a provider for Adverity on the registry, it won't be there. So you might have to search for it on GH perhaps.
Also if all that you want to manage is a Workspace, in the absence of a provider, creating a
dynamic provider for managing the Workspace resource could be a viable workaround. You can make HTTP requests to
Adverity's public API. There are examples showing you how to author one yourself.