Question about dependabot shared module update PRs

By default, dependabot will open update PRs whenever new commits are created in the shared-modules Flathub repo.

I want to make it open PRs only when updates are available for shared modules that my app uses.

Is the following configuration correct in order to achieve that, or do I need to add something else? I couldn’t find a clear answer elsewhere.

version: 2
updates:
  - package-ecosystem: gitsubmodule
    directory: '/'
    schedule:
      interval: weekly

    # Make dependabot open PRs only when updates are available for the following shared modules:

    allow:
      - dependency-name: shared-modules/SDL2/SDL2_image.json
      - dependency-name: shared-modules/otherlib/otherlib.json

Also, after adding dependabot.yml, it would be enabled right after merging the PR? Cause some Github documentation says I need to also go to repo settings to enable it, but app maintainers don’t have access to their app’s Github repo settings.