You need to remove that container and recreate with the \ back in the run line.
You need to find the real reason why you are getting the above errors with the correct manner and format of your domain.
I am only saying this as now I don’t think there is a fix to your system until you do so.
If the double backslash was wrong then nobody would be running Collabora via the instructions given. I am and so are many others.
I am on Debian and apart from the problem with Aufs and swapping to device-mapper and with self hosting managing your subnets DNS as the docker client is also a subnet client which many overlook.
It works fine and generally much of the errors are config error and confusion over the subdomains, dns and Aufs.
The problem is there is disagreement about Aufs support in the main Kernel so we are not all on the same playing field and Docker is very Distro affected.
I spent a week scratching my head and to be honest if it wasn’t for a bit of help from @Ark74 I would of been stuck.
It caused me so much of a headache I did a noob tutorial by a noob, I used to be a sysadmin but that was almost 20 years ago and the install with hindsight maybe should mention a few things.
That is for Debian Jessie with Ubuntu Xenial (16.04 +) if you install linux-images-extra and linux-images-virtual Ubuntu supports Aufs and I think it works well.
sudo linux-image-extra-$(uname -r) linux-image-extra-virtual doesn’t exist for Debian but this should work.
Run from there repos and get the most current.
So no need to swap to device-mapper as background storage.
If you are going to run with different config setting as you propose with all the differences distro’s seem to bring we are likely going to be unable to help each other as our systems will be very different.
This is very true with Debian and the info Docker are sharing is cynical in my mind.
With this little bit of info that is relatively worthless and ignore the rest unless you are going to swap device-mapper for aufs support.
Enable the backports repository. See the Debian documentation
Ok what am I supposed to do with the backports? The fact of the matter is Docker uses Aufs and Debian have removed it from the mainline Kernel and Docker don’t want to mention this.
So depending on distro we are not all the same, hey you can edit the instructed methods that work for many if you want.
But check how Docker should be installed on your distro and just like apache / mariadb / php it may have distro differences that are out of the scope in nextcloud install instructions.
docker ps -a #list all containers.
docker stop [container-id] #stop container
docker rm [container-id] #delete container
docker images #list all images
docker rmi [image-id] #delete image
docker exec -i -t [container-id] /bin/sh #run shell inside container
docker logs [container-id] #view log
docker info #environment setup
https://docs.docker.com/engine/reference/commandline/docker/1
Check your DNS on the server and inside the container.
nslookup example.com
Check your certs on the server and inside container.
openssl s_client -connect example.com:443
That is about the best I can do and I am actually wondering why the Nextcloud guys are not publishing this info as many people are landing as noobs with nextcloud and leaving with the feeling it is an unsolid product, which it isn’t, but how daft is that?