That is not correct. You just need some conversion to get MEL to work on ATV.
Plex displays wrong colours with Dolby Vision on AppleTV 4k - #411 by sw_5163
As for FEL, I recommend using your C7’s internal player. It’s been proved C7,C8,C9 can play FEL file. You may want to check the Dolby Vision Stuff under @RESET_9999’s signature. There’s a huge discussion regarding this on MakeMKV forum.
