It’s probably down to your TV’s audio settings. Which tv do you have? 

thank you for your response. I own a TV: LG OLED55C9PLA

I assume the Kodi App is not available from the LG store, so is it installed on another device connected to the TV - have you set that connected device to play Dolby Digital (Plus) 5.1 audio? and set the TV to ‘Bitstream’ and ‘Pass through’ on its ports?

Thank You. Its correct. Another device - Xiaomi Mi TV Box S EU

Bitstream’ and ‘Pass through’?

No. I didn't do anything like that. could you please advise me how to do this?

Goto the C9 TV ‘Settings/Sound/Additional Settings’ and set the port in use by the Xiaomi Mi TV Box S EU to Bitstream.

Goto ‘Settings/Sound/Sound Out and set the HDMI-ARC connection ‘Digital Sound Out’ to ‘Pass-Through’.

If the above doesn’t solve it, then it’s likely the sound-out settings on the Xiaomi Mi TV Box - which I don’t personally know too much about …and you will need to consult it’s ‘User Manual’ for its sound-out settings, or perhaps ask on their support forum.

thank you very much.  I appreciate it very much.  I'll try tonight and let you know.

Good day.

So I bring the promised information. I already had your recommendation set up from before.

I tried a Netflix movie on the Xiaomi device and it sounded similar to the Netflix app on the LG TV.

So it looks like the problem will be with the KODI app.

*I found in the TV another settings: DTV sound settings (MPEG, Dolby digital, Dolby digital plus, HE-AAC, Auto). should I choose Auto?

I have another question.

Do you have experience with the device: NVIDIA SHIELD TV PRO (2019)?

Thank you

Yes ‘Auto’ should be absolutely fine, but you could also try DD+ or even Dolby Digital, just to see if it makes any difference.

I have experience with Nvidia Shield TV - the bar-shaped version of their product,  but not the Pro version.

I suspect it’s the Kodi version of the App too, but are there any audio-out settings you can perhaps change in that App?

I was curious and made a small attempt.

I went through the older movies I watched through Kodi and came up with the following.

Kodec AC3 5.1 - movies boiling point, Marcel The shell, it works

X

Codec AAC 5.1, DD+ 5.1 (side) - movie John Wick 4 - does not work, switches to stereo PCM.

Do you have any insight on this?

Next, I found Kodi's internal audio settings. i enabled all available formats including DD+ but it didn't work for John Wick 4...

And does the Dolby digital plus codec work on your nVidia Shield device?

I have my Nvidia Shield sound out set to ‘Auto’ if I play John Wick 4 from the Amazon Prime App on that device, I get this audio output in the Sonos App via my LG C9 TV (See attached) 

mmm, probably time to buy a new device... thank You Ken for your concern!

I note that you’re in Czechoslovakia. Make sure that the language track you are watching is in the correct format…they aren’t always so.

Czechoslovakia has not existed for thirty years.  now it is the Czech Republic and Slovakia

Hello.

I found one interesting thread with an answer here, see below. thanks to this setting, Xiaomi can also play a movie with Dolby Atmos. I don't understand, something between heaven and earth…

Best answer by marksawbo

Kodi 5.1 Audio Setup

1. SystemSettings>Audio

2. Numberofchannels=2

3. Outputconfiguration=BestMatch

4. StereoUp-mix=OFF

5. Maintainoriginalvolumeondown-mix=ON

6. Boostcentrechannel=OFF

7. Re-sampleQuality=HIGH

8. KeepAudioDeviceAlive=10minutes

9. DSP=OFF

10.Pass-through = ON

- Also turn on the two DD AC3 options.

11. In video settings > Turn on Adjust Display Refresh Rate = On start / stop 12. Pause during refresh rate change = 3 seconds

Of course, you’re right, and you do have my apologies…,

Go to Settings/Sound/Sound Out and set the HDMI-ARC connection ‘Digital Sound Out’ to ‘Pass-Through’. And I set to automatic , now it’s change to Dolby digital 5.1!