How is your RPi connected to the soundbar?
For case 1 your TV and the soundbar must be connected via eARC not only ARC to support high bit rate audio at the return channel. Sometimes it's only available at a specific HDMI port and maybe additional configurable in the settings of the TV.
In the second case, do you have ensured that you set the audio channels to 7.1?
You are right that some issues were corrected (in worst case introduced 
) after 12.0.1 release and a recent nightly build may work better, but it's more helpful when you enable debug logging, reboot and provide a link to the log.
Hi silentsound, be sure to switch to EXPERT MODE in Kodi settings, go to Settings/System/Audio and "Enabled passthrough" for all containers including TrueHD and DTS-HD.
The reason you're getting Atmos is maybe related to the audio container of the file (DD+ instead of TrueHD).
For streaming services (limited bandwidth) there also DTS:X lossy available. Maybe such kind of material ends with DTS only.
