I work on calling for Signal, and the last few months we have been working on desktop calling. It's nearly ready and will hopefully be in public beta in a matter of weeks, and (again, hopefully) fully available in a few months.
This is excellent news. (Desktop calling would include video calls, right?)
There is an option in settings to enable camera and microphone, no? Have you tried that?
I have those enabled, but I don't see a way to make a voice or video call from the desktop. Maybe I'm missing something?