One way to go about this would be writing a custom
launcher application that opens a window, but never calls `Run` on it, leaving it hidden and allowing to implement a custom main loop, which can omit all rendering and audio.
Another option would be to run the launcher without a graphics or audio backend, either by
skipping the OpenTK ones via config, or by removing their dlls from the plugins folder. Keep the default system backend though. This would mean that there's a game running that
thinks it is rendering as usual, but actually ends up pouring its rendering data into the void.
I think the first option sounds a lot better so far, but maybe it helps to know that the second one exists. They're not mutually exclusive either.