If the authentik configuration should be handled by abra add the following to the env:

    COMPOSE_FILE="$COMPOSE_FILE:compose.authentik.yml"
    AUTHENTIK_USER_PREFIX=authentik
    AUTHENTIK_DOMAIN=authentik.example.com
    AUTHENTIK_SECRET_NAME=authentik_example_com_nextcloud_secret_v1  # the same as in authentik
    AUTHENTIK_ID_NAME=authentik_example_com_nextcloud_id_v1  # the same as in authentik

And run:

    abra app cmd <app-name> app set_authentik