firestick and avr

hello so i got a firestick set to.dolby

and it still says pcm on

and then i go in to kodi and change settings pasthough, tick ac3, optimised, 5.1, also tried 2.

and the avr never changes from pcm, if i change it too fix, it changes too pcm with 5.1 showing

but i still think it still plays in stereo

i understand or i might be wrong that the firestick can’t do dts.

will it change too dolby if i played Dolby fire.

or is it normal for the kodi menu too stay at pcm

also with fire stick settings as dolby hdmi

will YouTube play dolby or bbc iPlayer

will it change from pcm too Dolby

the kodi is 17.1

and the avr can play all files, 1080p passthough