While there are many "closed caption" options available for streaming, They usually involve a twitch extension or an overlay that you put in as a source, rendering them mandatory viewing for all viewers.
Meanwhile, the existing OBS studio Closed caption (experimental) option works as a great CC option that viewers can turn on and off on stream, HOWEVER it is absolutely abysmal to the point of I only used it as a joke. It just doesn't recognise Australian English at all, even if you train the Microsoft Speech Recognition in Windows.
This completely changes the game and I have been waiting YEARS for someone to make it. If you are a twitch streamer, make sure to put a tag on your stream for "closed caption" so our hard of hearing viewers can benefit!