Auth0 OpenID Connect
Use "custom" server template with full discovery URL: "https://12id.eu/.well-known/openid-configuration"
Auth0 JWT.io debugger
Copy-paste the returned "idtoken"-value here to decode and verify the meta-data.
Google OAuth 2.0 Playground
Use "server-side" OAuth flow and "custom" OAuth endpoints with authorization EP = "https://12id.eu/" and token EP = "https://12id.eu/p/oidc/token$"