I'm a bit confused.
Most people get confused with Docker and containers so don't sweat it ![]()
Containers virtualise an app within a supporting environment. In our case the app binary is 'make' although this is not that clear unless you understand how our buildsystem works.
The docker steps are correct. The info that's probably missing is an instruction to git clone the LE sources first.
Then you need to 'docker build' the container by 'pulling' from a docker source. This is a local Dockerfile and not a URL or a pre-built container from the online docker 'hub' repo. From a cloned LibreELEC.tv source folder the source files are in tools/docker/
Then you need to 'docker run' the container, with the run command providing instructions to the docker runtime on directories to map, and buildsystem variables (PROJECT=X, DEVICE=Y, ARCH=Z, etc.) that are passed to 'make' to define what image to create.
It might be easier to run an Ubuntu server LTS release VM under proxmox and SSH into that environment to install dependencies, clone sources, and build using the CLI commands that you can see in the normal build instructions. The main reason we support Docker building is for our own CI use-cases building nightlies etc. .. not because it's a better/easier option.