Creating a Modern Team Site using the SP API via App Only Tokens does not work. In order to create a Modern Team Site you must use Microsoft Graph API to do this. So use our Graph module instead of the SP Module.

You can see the Microsoft docs here.

https://learn.microsoft.com/en-us/sharepoint/dev/solution-guidance/security-apponly#what-are-the-limitations-when-using-app-only

In case this link goes bad, it says: "Creating modern team sites does not support app-only when you use the SharePoint API for it."

We've noted this in our docs as well.

https://pnp.github.io/pnpjs/sp/sites/#create-a-modern-team-site