How Do I Watch My Videos in Samsung Apple TV App?

What about the TV app on my iPhone? None of my videos show up there either, only the purchased ones. They used to, in iTunes, before the TV app. So my only option now is Airplay from my computer (which is nowhere near my TV)?

Media Sharing is NOT an option for me in Sharing Preferences.

So I copied the movies to my iPhone, and then tried to stream them to my TV via AirPlay. However, when I turn screen mirroring on and start a movie playing, my phone (the TV app) tells me, "This video is in a format that can't be streamed to this TV." The videos are in .MP4 format.

I got out my old Apple TV (3rd gen), and connected it. I can no longer use it to connect to my computer. It tells me to turn Home Sharing on, but that is not an option for me (macOS 10.14.6). This used to work. I also tried AirPlay to the AppleTV (instead of to the Samsung TV), and it partially works. I get audio with a black screen. This too used to work.

Unless there is some other format/codec I can try, I'm out of ideas. It kind of sucks that these things just stop working.

Looks like the solution is to put the videos (H.264, AAC) on my old iPad Air (1st gen), then AirPlay from the iPad to my old Apple TV (3rd gen), which is connected to my new Samsung TV. It just works! I can see the video and hear the audio, and it looks/sounds good!! Lesson learned: Upgrade and lose functionality.

Just to clarify, MP4 format using the H.264 and AAC codecs. That format is supposed to be supported for AirPlay on iPhone, iOS 14.6.

I can AirPlay the videos from my computer (macOS 10.14.6), but they are pixelated and jerky, not really watchable. (It would be nice if these posts could be edited.)