docs: Add link to matrix.org federation tester

docs/deploying/generic.mdx

@@ -268,9 +268,13 @@ to the `#admin:example.com` room and be able to [issue admin commands](../refere
 
 ## How do I know it works?
 
-To check if your server can communicate with other homeservers, use the
-[Matrix Federation Tester](https://federationtester.mtrnord.blog/). If you can
-register your account but cannot join federated rooms, check your configuration
+To check if your server can communicate with other homeservers,
+use an external testing tool:
+
+- [Matrix Connectivity Tester](https://federationtester.mtrnord.blog/)
+- [Matrix Federation Tester](https://federationtester.matrix.org/)
+
+If you can register your account but cannot join federated rooms, check your configuration
 and verify that your federation endpoints are opened and forwarded correctly.
 
 As a quick health check, you can also use these cURL commands: