In the screen capture that Ron showed above, he is trying to get you to try viewing the channels that are flagged with the green 4 to rule out that possibility.
There already is a Tech Support ticket open and in their possession.
Conjecture and speculation are inadequate debugging tools.
But I agree customers should not be debugging to begin with.
I did test H.264 on Android phone, LGTV and Fire Stick 4k G2 and they all worked fine using the latest firmware version with MPEG4.
Usually they have no problem with playback of recordings. Those are H.264 anyway. On some devices they block the scan portion.
When you only get audio from OTA broadcast it’s a clue. It may be MPEG4 and the device isn’t decoding the video.
H.264 is the format - MPEG4 is the documented standards.
But Apple is special. To be clear