Microsoft brought back the ability to show the time with seconds in the Notification Center for Windows 11 as seen on youtube. Enable this feature by opening Settings > Time & language > Date & time, and turn on “Show time in Notification Center.”
If the option is not available in your settings, try running Windows Update and this github command vivetool /enable /id:42651849,48433719 as administrator then rebooting.
More detailed instructions are available here and here.
