You would use jsinterop to call a javascript based video library. the library will make use of the browsers audio and video support (WebRTC):
https://developer.mozilla.org/en-US/docs/Web/Media/Audio_and_video_delivery
not familiar with Jitsi, but it has javascript WebRTC component that should be usable from Blazor.
note: you will probably need a server application to allow clients to find each other and communicate. the Jitsi server components are java based.