If you have a 7.1 speaker set-up - you want 7.1 not 2.0 enabled in your sound settings.
Also if you want DTS HD MA and Dolby True HD to be losslessly decoded, you will need to disable DD and DTS passthrough, as otherwise I think it will bitstream passthrough the lossy DD/DTS core/secondary streams rather than decode the lossless DTS HD MA or Dolby True HD losslessly to PCM 5.1/7.1.
You won't get Atmos until HD Audio bitstreaming/passthrough is supported on the Pi 4B - PCM lossless decode is only for Dolby True HD and DTS HD MA - not Dolby True HD with Atmos or DTS:x. (You may - possibly - get DD+ with Atmos - but that's not intentional and usually only used for secondary language audio streams on BD/UHD BD)
If you must have Dolby True HD with Atmos, the Pi 4B isn't currently for you.
However if you want the best quality audio possible with a Pi 4B currently - disable passthrough, configure for 7.1 if you have 7.1 speakers (i.e. Front R,L, Centre, Side R, L and Rear R, L + Sub) or 5.1 if you have 5.1 speakers (note I'm ignoring 7.1.2. or 5.1.2 Atmos in this - if you have 7 speakers but 5.1.2 then configure for 5.1, if you have 9 speakers in 7.1.2 then configure for 7.1)
thanks for answer. I always had enabled audio passthrough and wanted to do all decoding in my receiver.
So passthrough isn't supported at all?
Is there any time window when it will be supported?