Back in the early 2000s I had the idea for a desktop OS where the local apps were all just http servers, and every OS “window” just a “browser”.

My original idea involved a custom markup ui language akin to WPF because at the time HTML was not nearly as up to the task. HTML could probably handle it today.

Between Electron, WebOS and ChromeOS some of the ideas have been tried but not to as high of a degree.