Mount directory of Nextcloud-container to Spreed-container

I have currently set up 2 LXD containers. In one is the Nextcloud installation. In the other I have just installed spreed-webrtc. I noticed that spreed-webrtc needs a direct resource from nextcloud.
I followed (this guide) so far, and I fail at this point:

Next you need to start a new Spreed WebRTC container and also mount /var/www/nextcloud/apps/spreedme/extra/ to the container.

I don’t know how to do this with LXD containers. I thought of some sort of a magical symlink, but I don’t know how if that would work.

Can you help me?

I found a solution that probably works.
Execute this outside of the containers to do black magic:
lxc config device add spreed-webrtc nextcloud-spreed-extra disk path=/var/www/html/nextcloud/apps/spreedme/extra source=/var/lib/lxd/containers/nextcloud/rootfs/var/www/html/nextcloud/apps/spreedme/extra/

I never did such a cruel thing before. This adds a mountpoint to the spreed-webrtc container which refers to the absolute path from the nextcloud container. Sadly the device is read-only. The server behaves odd and doesn’t show the usernames and profile pics. (Only sometimes) Screensharing works though.

I want to do it correctly. How did you set up your containers? Did you put Nextcloud + Spreed WebRTC in the same container?

Why not use our Docker image? See https://github.com/strukturag/nextcloud-spreedme#installation-with-docker

Docker works fine in LXD containers, but make sure to use the ‘docker’ profile for your LXD container: https://stgraber.org/2016/04/13/lxd-2-0-docker-in-lxd-712/