How to always run a sequential, final job (e.g. Slack notification)?

I’m searching for a solution to run a final job always, i.e. no matter if the previous jobs in a sequence failed. Basically a when: attribute of steps, but as a workflow’s jobs setting:

workflows:
  jobs:
    - nice-orb/nice-job
    - slack/notify:
        requires:
          - nice-orb/nice-job
        when: always  # <- This seems not possible, or?

orbs:
  slack: circleci/slack@3.x  # notify job not there, yet

Without such setting, it would be impossible to use any job of an orb and receiving a notification of the job results with the new UI.