Owncast
Overview
Owncast is a free and open source live video and web chat server for use with existing popular broadcasting software.
Simulcast
By default, when you set up streaming software, it will only stream to your Owncast instance. If you want to simultaneously broadcast to various services, you'll have to either use something like Restream or you can also use FFMPEG.
YouTube
With your brodcast stream started, use the following FFMPEG command to simulcast to YouTube.
ffmpeg -v verbose -re -i https://YOUR-OWNCAST-SERVER/hls/stream.m3u8 -c:v libx264 -c:a aac -f flv rtmp://a.rtmp.youtube.com/live2/YOUR-STREAM-KEY
This command will copy the video and audio feeds from your HLS Owncast live stream and forward them to YouTube.