From an existing answer on another thread: Huffman1132 Q (Jan 17, 2020), answer by kslksl (Feb 18, 2020), hopefully linked correctly...
"I just finally figured this out as I was facing the same issue and movies downloaded on our mac computer would not play on our Apple TV.
I went to TV app > Preferences > Playback and made sure both "Download Multichannel Audio" and "Download HDR when available" were unchecked. When I restarted the movie download it came down as an m4v file."
I tried this on my Mac and it worked to switch download from movpkg (pre-change) to m4v (post-change). My issue, if anyone has an answer, is how to do this setting on an iPhone or iPad, which are also downloading movpkg. I use my iPhone to download from out-of-home download locations and then copying movies back to my Mac at home. Until I can get my iPhone or iPad to download m4v files, this route to get around my (ex-urban) limited at-home internet is problematic. I tried various settings, and none have worked.