Hi everyone,
I've been browsing this forum with no luck about this.
I want to use Tidal Connect in a similar way Librespot is implemented in LibreElec.
A binary exists for this but needs outdated libraries, so a guy made a docker container with those libs: https://github.com/TonyTromp/tidal-connect-docker/
This container works fine in LibreElec when the sink is not locked by Kodi.
(I have been using --device /dev/snd to get the container access to the sound device)
However, I had no luck trying to make it use PulseAudio in any way, so the sound could be mixed with Kodi. (this is how Librespot works in LibreElec if I understood correctly ?)
After stumbling upon this post:
Docker container's audio to OS
From: escalade
If you want to use Pulse you can run your container with -v /run:/run -e PULSE_RUNTIME_PATH=/run/pulse, I think that should do it.
I've been trying to bind /run/pulse in many ways to the container, eventually succeeding in seeing a pulseaudio sink (named librespot) from within the container but no way to use it.
Would anyone that understands better PulseAudio and ALSA than me have any idea on how I could have a Librespot-like client to output audio simultaneously with Kodi please ? 
Thank you for your answers.
Keep rocking, LibreElec is a great distro, been loving it for years now !