I am living in my RV without wifi other than cellular data so I relied on this to watch Netflix, Hulu, HBOMax on my phone using unlimited data. Not No Mo since the update.
I think it was intentional at the behest of the cell companies. They couldn't stand that people were using unlimited data to stream on their tv's using the cable, instead of paying for a mobile hotspot and an additional data plan. They KNOW that most people would rather watch on their tv instead of a phone screen, so they shut off the capability to do so. Dinrail nailed it with his comments. I think streaming with unlimited data using the hdmi dongle is history. Apple needs to disclose that on the packaging and marketing for the cable--that it will work with many apps, but NOT most streaming tv services.
In any case, I did find a workaround that is a bit of a pain, but doable.
Using your unlimited data, download your shows on the various apps. My iPhone 13 is 1 TB so I have plenty of memory. Then, put your phone on Airplane mode. Then play the downloads on your tv via the cable. This works for me with Netflix and sometimes HBOMax. With Hulu, I only get video, but no audio, so that's a bust.
Not sure who to credit with this hack, I read it on one of these forums somewhere. So it provides 'some' relief at least for Netflix.
What a freaking hassle.