> google's official response: Root Cause: It's likely that Apple's media player no longer supports the vp08 coding format, leading to the playback issue you're experiencing. This isn't necessarily due to a file type incompatibility, but rather a specific codec incompatibility within the MP4 container.
That response sounds weird because as far as I know, macOS has never supported VP8. Furthermore, VP8 supports only .webm and .mkv movie containers which as far as I know, macOS has never supported neither.
...
I just tried to encode VP8 in a .mp4 container and ffmpeg refuses to do it:
ffmpeg -i input.mp4 -c:v libvpx -c:a aac -b:a 128k output.mp4
Could not find tag for codec vp8 in stream #0, codec not currently supported in container
ffmpeg -i input.mp4 -c:v libvpx -crf 10 -b:v 1M -c:a libvorbis output.mp4
Could not find tag for codec vp8 in stream #0, codec not currently supported in container
But that succeeds to a .mkv (.webm needs Vorbis or Opus audio) and IINA can play that OK:
ffmpeg -i input.mp4 -c:v libvpx -c:a aac -b:a 128k vp8_aac.mkv
ffmpeg -i input.mp4 -c:v libvpx -crf 10 -b:v 1M -c:a libvorbis vp8_vorbis.webm
ffmpeg -i input.mp4 -c:v libvpx -crf 10 -b:v 1M -c:a libopus vp8_opus.webm