I'm not sure why people keep spreading this misinformation. This does not work. You have to start the livestream from youtube studio.Check out this post:
Can't automatically start streaming
I am testing out starting OBS automatically to start streaming when opening OBS using a .bat file. I found the launch parameters and created a .bat file. I set everything up for Youtube streaming. Every time I launch OBS using the .bat I get the following error: Looking at the logs, it says...obsproject.com
Disconnect from your YouTube Account in Settings/Stream/Destination. Use your stream key instead, which you will find in YouTube Studio.
After doing this, the Manage Broadcast button will disappear. Just start and stop the stream from OBS with the preferences that you setup in YouTube Studio.
Best.
I'm imagining you guys are all starting a live stream to get your key to 'test' this. Youtube waits awhile after you open this page to receive a broadcast.