Yes, SharePoint Workflow Manager was cancelled before it reached RTM status. See https://learn.microsoft.com/en-us/sharepoint/what-s-new/what-s-deprecated-or-removed-from-sharepoint-server-2019#sharepoint-workflow-manager-sharepoint-server-2019-preview.
What happened to SharePoint Workflow Manager? Was it cancelled?

Green Arrow
41
Reputation points
In this post from July 2018, Mike Lee from Microsoft mentions a new component called SharePoint Workflow Manager (SPWFM) to replace the existing Workflow Manager. But it seems the product was cancelled or retracted before it was ever published?
In October the same year, Trevor Seward concluded that "there is no new version of WFM" and directed people to the existing Workflow Manager and Client tools.
What happened? Was all workflow love directed to the Data Management Gateway to get people to use M365 Flow with on-prem data?
Accepted answer
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Trevor Seward 11,491 Reputation points Microsoft MVP
2020-08-31T23:32:02.617+00:00