The October 2018 Update was re-released in November but was only available to a certain subset of devices without any compatibility issues. In the last 24 hours they have updated the Windows 10 Update History page with the following note:
Rollout Status as of December 17, 2018: Windows 10, version 1809, is now fully available for advanced users who manually select “Check for updates” via Windows Update.
These advanced users Microsoft mentions here are also referred to as “seekers” by the company. This means if you go into Windows Update and click the Check for updates button you should begin to receive the October 2018 Update. The only exception to this would be if your system still has a block in place by Microsoft due to an identified incompatibility issue.
Note: Those blocking items are listed on the Windows 10 Update History page.
No systems set to only receive automatic updates will get the October 2018 Update until a later date determined by Microsoft.