I can search for existing issues and even vote on issues.
However I can’t see a way to create a new issue. So what’s the correct procedure?
I see I can submit a bug via Unity’s Help menu directly, but this submits the report to fogbugz, as a private issue, not to the Issuetracker. Also, the Unity bug reporting tool is tailored to reporting bugs with the Editor or the Player, but I want to submit a bug about a specific package (Input System).
I believe the bug reporter is the way to do it, and it’s up to the Unity staff who review your bug to decide if it’s something worth adding to the issue tracker themselves.
I believe you are correct. Of course Unity QA and developers can create new issues themselves, but they will only do that if they were the ones who found the issue.