Signaling is a very app-specific question, as you can use a wide range of options. If you take a look at the "apprtc" example, it's a demo which uses appr.tc's signaling.

You can indeed use aiortc facing a browser, itself or any valid WebRTC endpoint.

Sure, you can use aiortc for a desktop application. However for this specific usecase embedding a browser which supports WebRTC (say QtWebEngine) might be a good option too.