Do you use AMD or Intel graphics card?
I answer to myself: It's this Intel processor graphics.
Did you had a look at BIOS / EFI settings? Maybe you'll find a tweak for DisplayPort.
While playing Atmos, did you had a look at "Audio and subtitle settings", which is part of the playback bar on the bottom. That menu also has an "Enable passthrough" switch.
What's the "Passthrough output device" on LE settings? Do you have multiple choices?
Because GUI sounds are affected, try to play Atmos with disabled "GUI sounds" on LE's audio settings.
Do you use AMD or Intel graphics card?
What do you need from me?
Well, you could spend money. 
What do you need from us?
What do you mean a current nightly? Sorry for being so dense...
That's progress. It makes me thinking, it's not a software bug, but the HDMI cable (NUC -> AVR). Bugs usually don't behave like this.
Maybe it was working on Win10, because you had a lower screen resolution. This reduces the HDMI data rate, so there is enough room for Atmos data.
Try another HDMI cable, which is made for 4K (HDMI 2.0 or 2.1 standard).
There are some apps to control Kodi. Maybe it's worth to test with an app, and disconnected projector.
Can you test Atmos with a regular TV? Maybe it's an HDMI routing problem. If your projector has audio options, play with them.
Thanks for this info. Then it seems to be a bug on LE, and I'll look at the logs again.
And as already mentioned on the windows 10 instance with kodi installed, ATMOS did work...
Win 10 on the same NUC?
My setups were always the same HTPC -> AVR -> Projector, since i don't like to deal with ARC or eARC
That's fine. If you have more than one HDMI inputs on your AVR, try another one. Here is the story: Click!
2022-05-09 20:18:50.812 T:1166 ERROR <general>: AddOnLog: inputstream.adaptive: License server returned failureThis error and your screenshot (Widevine CDM never installed) makes me thinking, the download failed.
If you search for "Widevine" on this forum, you'll find instructions how to manually download and install.
Had anybody got this addon working ?
Yes: Click!
I have 10 different HDMI ports to choose from in the Passthrough list. I tested them all but with the same result as before...
I also changed the channels form 2 to 5.1 and 7.1 but no improvements on this side as well
Why does libreelec see so many HDMI ports? There are not 10 ports on the device...
Good point. I only have a TV connected over HDMI, and I have 5 audio output options in total. So your additional output options exist, because you have a TV and an AVR connected in a chain.
The order of that chain can be important. So if your current setup is NUC -> TV -> AVR, try NUC -> AVR -> TV.
During the "live" tests (booted from an USB drive) I had to play from the same USB stick that I booted from.
Otherwise I "stream" all my Media over my 1GB network connection the same way I did when I tested kodi in a windows instance.
Makes sense.
Please check pass-through activation again. Use the default skin, and activate "Expert" settings on LE's audio settings.
Try different audio output devices (HDMI MAI vs. MEI). Also try more than 2 output channels.
The debug logs are still a puzzle to me, because they have kernel errors. I'll have another look, soon...
Do you play from external SanDisk USB drive? If yes...
The issue appears on high-data-rate audio, so your external USB drive might be too slow.
a) reformat the USB drive to EXT4 (maybe LE doesn't like the current FAT format)
b) use a different USB cable
c) use a different USB drive with faster read access
It occurs to me that I am currently connected to a 1440p monitor. Could that be an issue?
That's above Full HD, so a high speed cable could already be necessary.
