You can now link support requests in Plain to issues in GitHub! This allows your team can link a thread to an GitHub issue (or create a new on from within Plain) when this issue moves to closed it will bring that thread back to Close the Loop where you can follow up with the customer to let them kno wit's shipped.

To start using this, Go to Settings → Integrations → GitHub.
You can find more details in the documentation.

Not using Github Issues? You can also link Linear, Jira or Shortcut issues