ffmpeg
Streaming with ffmpeg is quite easy. You can stream any connected webcam or HDMI grabber that appears in /dev/video* and incoming alsa audio devices. In this example, the /dev/video2 video device and the hw:1,0 alsa audio device are used:
ffmpeg -f alsa -ac 2 -i hw:1,0 -thread_queue_size 64 \
-f v4l2 -framerate 60 -video_size 1280x720 -input_format yuyv422 -i /dev/video2 \
-c:v libx264 -preset veryfast -b:v 1984k -maxrate 1984k -bufsize 3968k \
-vf "format=yuv420p" -g 60 -c:a aac -b:a 128k -ar 44100 \
-f flv rtmp://<ip-of-your-server>/live/<your-streaming-key>