This docker mod helps you with automatically trusting new certificates that are added to a special trusted-certs config folder.

Add your certificate with an extension of a .crt to container's /config/trusted-certs folder, and as a result, it will be trusted within the docker container.

version: "2.1"
services:
  service-name:
    image: ghcr.io/linuxserver/service-name
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=Europe/London
      - DOCKER_MODS=samuelbartik/trusted-certs # <---
    volumes:
      - /path/to/appdata/config:/config
    restart: unless-stopped

The new certificates are copied to /usr/share/ca-certificates folder and appropriate entries are added to the /etc/ca-certificates.conf config file. After that the store is updated by running update-ca-certificates command.

The mod is not tested on all base images and thus might not work. As of right now, there is no way to detect the deletions of files from the /config/trusted-certs folder and automatically reflect those changes in the container. The certificate needs to be removed manually, or the container needs to be re-created after deleting a certificate from the folder.