Awesome tutorial.
However, in case anyone is trying to run Nextcloud + Collabora inside Docker on and old Debian machine (8 or older), I banged my head against the wall for hours with Collabora failing to respond until I found my way to this answer:
https://help.nextcloud.com/t/collabora-docker-capabilities-problem/4774/10
One simple line in a daemon.json file:
{
“storage-driver”: “devicemapper”
}
…restart docker service, and Collabora suddenly sprang to life and started responding. Problem solved.