I could not find USB file type compatibility anywhere, so I tested all audio and video file types to see which were compatible with my June, 2020 build Model S. Here are the results:
Media Supported on USB in Current Tesla
Audio
AC3 NO
AU NO
FLAC YES
M4A YES
MP2 NO
MP3 YES
OGG YES
OPUS NO
WAV YES
WMA NO
VIDEO
NO SUPPORTED FILE TYPES
Media Supported on USB in Current Tesla
Audio
AC3 NO
AU NO
FLAC YES
M4A YES
MP2 NO
MP3 YES
OGG YES
OPUS NO
WAV YES
WMA NO
VIDEO
NO SUPPORTED FILE TYPES