JWPlayer still works for us (though not sure if it's "open source" anymore). The player component speed always wins hands down when we re-test options. https://github.com/jwplayer https://developer.jwplayer.com/

I'm a fan of acestream: https://github.com/magnetikonline/docker-acestream-server & http://acestream.org

There are a lot of different options, but depends on what you are looking for!

* What are your goals around latency

* What does the publishing/viewing look like (want to watch in the browser) do users need to upload?

* Do you have any restrictions around codecs or bandwidth?

ffmpeg + nginx-rtmp-module & nginx ? Depends on your needs and how complete of a solution you want.