I’ve tried that same thing a few months ago.
At first, we were looking into adding libmediasoupclient as a library to Unity but after reading this post I didn’t like that approach anymore (I am mostly familiar with Node-land and my C# colleague didn’t seem to think he’d be able to do it).
If that post doesn’t scare you, go for it. If it does, there’s always the possibility of using “Vanilla” WebRTC (e.g., MixedReality-WebRTC) and bridge it to be Mediasoup-compliant. This is what we went for with some success. We got the connection to Mediasoup server working and Video was transferred perfectly. However, we were faced with a problem we were not able to debug regarding Audio transmission. I’m not saying it’s impossible but unfortunately this was a show-stopper for us, considering that the MrWebRTC project has been put on ice and is not maintained anymore.
A third alternative, which we never went for, is to port SipSorcery to work with Unity and bridge it to Mediasoup (same as MrWebRTC). But this also seemed like too big of a time investment.
After all, we scrapped the idea of this project because of these problems.
If you manage to get it working, though, I’d be very happy if you could share your path. 
Edit: I forgot to mention the Unity WebRTC implementation which probably is the easiest way to go (again with bridging SDP to Mediasoup). But for our use-case it didn’t work because we needed to build in UWP which this library did not yet support - there might have been some advancements since then, you should check it out.