theme.park/docker-mods/emby/root/etc/cont-init.d/98-themepark

#!/usr/bin/with-contenv bash

echo '-------------------------'
echo '|  Emby theme.park Mod  |'
echo '-------------------------'

# Display variables for troubleshooting 
echo -e "Variables set:\\n\
'TP_DOMAIN'=${TP_DOMAIN}\\n\
'TP_COMMUNITY_THEME'=${TP_COMMUNITY_THEME}\\n\
'TP_THEME'=${TP_THEME}\\n"

# Set default
if [[ -z ${TP_DOMAIN} ]]; then
    echo 'No domain set, defaulting to theme-park.dev'
    TP_DOMAIN='theme-park.dev'
fi

THEME_TYPE='theme-options'
if [ "${TP_COMMUNITY_THEME}" = true ]; then
    THEME_TYPE='community-theme-options'
fi

case ${TP_DOMAIN} in
  *"github.io"*)
  echo "Switching to github.io URL style"
    TP_DOMAIN="${TP_DOMAIN}\/theme.park"
    ;;
esac

if [[ -z ${TP_THEME} ]]; then
    echo 'No theme set, defaulting to organizr'
    TP_THEME='organizr'
fi

# Adding stylesheets
printf '%s\n' "@import url('https://${TP_DOMAIN}/css/${THEME_TYPE}/${TP_THEME}.css');" "@import url('https://${TP_DOMAIN}/css/base/emby/emby-base.css');" > /app/emby/dashboard-ui/modules/themes/light/theme.css
printf 'Stylesheet set to %s\n' "${TP_THEME}"