Single RTMP Ingestion Endpoint - How?

We run a small streaming business and one of our platform's biggest weaknesses is that we still have to setup unique custom RTMP ingest URLs for each client. The gold plated solution is obviously a single ingest URL, like Youtube uses, but I have searched high and low and just cannot seem to find any explanation of how it's done.

I'm guessing that there's some networking and DNS magic (Anycast?) involved, but there must also be some load-balancing done somewhere and if there is, how on earth do they scale load-balancers to handle the scale of multiple incoming streams? Is load-balancing load-balancers a thing??

I apologise if this is the wrong subreddit; if there's a more appropriate one, please let me know - I was thinking of posting in /r/webdev, but without more knowledge this feels like a networking challenge more than a software one.

Thanks!