This simply means the feature hasn’t been installed yet. Follow either Method 1 or 2 above. Windows does not install Telnet by default for security reasons. A Critical Warning (Please Read!) Enabling Telnet is generally safe for local, trusted networks (like your home or office LAN). However, never use Telnet over the public internet or an untrusted Wi-Fi network (coffee shop, airport, hotel).

Use this command instead:

How to Enable Telnet on Windows (10, 11, & Server): A Step-by-Step Guide

The best practice is to enable Telnet Client only when you need it for a specific troubleshooting task. Once you’re done, you can go back to "Turn Windows features on or off" and uncheck the box. This keeps your system clean and secure.