Previously I setup Settings>System>Network>Home Assistant URL pointing to DuckDNS, allowing me to access HA from an iPhone. Recently when accessing HA on a desktop browser, I noticed that attempting to access ServerControl displayed only a black window.
Using ssh, I removed the ssl_certificate and ssl_key entries from the config/configuration.yaml file, removed the Internet entry for DuckDNS in Home Assistant URL, set the Local Network to Automatic and rebooted the host.
But the ServcerControl is still displaying a black window with no data.
The server control and many of the other menus have been moved around in the latest few updates, so it is possible that your browsers are showing a cached page.
Try clearing the browsers cache.
I had customized the left panel navigation. I removed all of that from configuration.yaml and rebooted the host. Now I cannot find ServerControl anywhere!