send RMTP stream to server from browser (laptop camera)

Solution 1:

You need a media server to covert WebRTC to RTMP, please read this wiki, the stream flow is like this:

Browser --WebRTC--> SRS ----RTMP-+--> IVS
                                 |
                                 +-->FFmpeg --RTMP-> IVS

If you publish your stream to your media server, you could forward to IVS, or use FFmpeg to forward the stream to IVS.