You can temporarily directly modify the registry values that control the group policy setting. Group policy will automatically set these back to the group policy controlled values when group policy is refreshed, but this page shows you how you can use BatchPatch to temporarily directly modify the registry values.
https://batchpatch.com/using-an-alternate-wsus-server-for-batchpatch-windows-update-actions
https://batchpatch.com/using-an-alternate-wsus-server-for-batchpatch-windows-update-actions-part-2