Jean:
What can I do?
Well as audio routing is not the easiest thing to do you might just want to wait for a Bluetooth fix from OSMC team. Try if the current provided fix works.
I’ve now made some fixes available, and hopefully this will allow A2DP to work out of the box again.
Login via the command line
Edit the file /etc/apt/sources.list
Add the following line: deb http://apt.osmc.tv stretch-devel main
Run the following commands to update: sudo apt-get update && sudo apt-get dist-upgrade && reboot
Your system should have have received the update.
Please see if the issue is resolved.
I also recommend you edit /etc/apt/sources.list again and remove the line that …