Docker allows you to install all kinds of applications and services, the most interesting for LibreELEC are those that run headless, that is, without a local graphical environment (VPN servers, tvheadend, syncthing, ...). Applications that need a local graphical environment, for example Chrome, may collide with LibreELEC's graphical environment and may even be impossible to run.
Normal access to docker headless services configuration is via http from another device (and also through others: ftp, ssh, vnc, ...). For example, to access and configure the syncthing service, it will be normal to find it at http://<IP>:8384, the portainer service will be at http://<IP>:9000, the pihole service at http://<IP>:80, the jellyfin service at http://<IP>:8096, etc, where <IP> is the IP address of the LibreELEC device where the service was installed.
Does this clarify your doubts?
Note.- I have installed in LibreELEC a docker service called jellyfin that you may like, it allows sharing through DLNA the entire multimedia library and tvheadend satellite television channels with all the smart TVs in my house. To watch a Kodi addon from LibreELEC on another Smart TV, a player-addon that plays other addons via DLNA or Miracast would be necessary. This does not exist.