mediasoup-client requires react-native-webrtc >= 1.75.1. The fork you use is not in sync with that version, it’s done on older code. You can fork mainstream project and add getDisplayMedia.
If it works in p2p is because it uses old hacks no longer needed in 1.75.1. There was a huge refactor in that version. Not a bug in mediasoup-client.
I think I’ve help enough here given that you were using an experimental fork of react-native-webrtc without mentioning it into the topic discussion until I spent my time investigating it. I cannot do magic.