Ask HN: Live Video Streaming Providers?

Due to current situation many live events are finding a way to be consumed in a digital form.

What is the state of the art of live streaming video platforms? I remember many ages ago using Ustream with some success, but from what I see it has been bought by IBM.

I know live streaming today is offered by most social networks (Facebook, Youtube, Instagram, Periscope, etc). But I'm looking for B2B white label providers, capable of many thousands of concurrent viewers, that also offers some kind of SLA.

Do you have any direct experience or general recommendation?

Thanks!