You can ask Streamlink people to write a plug-in, if there are many
people like you interested in that website, they may do it.
https://github.com/streamlink/streamlink/issues
By the way broadcast that you are looking for may be already on one
of the sites they wrote plug-in for.
I started a thread before you named: streamlink: an up to date fork of livestreamer.
It has 224 hits by now.
Your thread has 505 hits by now.