Deploy on gitlab-pages of upstream project

Is it possible in a Multi-Project-Pipeline strategy, to let a downstream job deploy content on the upstream gitlab-pages?

For a “regular” pages deployment one just has to:

pages_deployment_job:
  script:
    - do some stuff with upstream UPSTREAM CI ACCESS TOKEN to retrieve data
  artifacts:
    paths:
      - public

and I’m asking myself if there is a way to do something like:

...
   artifacts:
    paths:
      - UPSTREAM_REPO/public

My goal is to prevent the need to configure a runner for upstream repositories.
The (already do) just trigger downstream “service” pipelines which push back information to the triggering upstream repositories.

Thanks for your help!

Not that I am aware of. Jobs are always run in scope of the project they are defined in.

There might be some way if you call GitLab APIs from the downstream job, but I am not sure it’s possible.