Hi @deLingniresTanguy-2346,
I did hear from the product team and there isn't an ETA just yet. Although Authentication/Authorization currently works for single containers, there's still work being done for Multi-Container apps as it's still under Preview. I know this isn't the answer you wanted to hear but team is working hard to finalize the multi-container feature set.
I encourage you to leave any feedback you may have here or over on https://feedback.azure.com/forums/169385-web-apps.
Regards,
Ryan