There was a recent release of a new Workflow Manager for all versions of SharePoint on-premises, so also therefore, for Project Server. Josh Roark, one of my SharePoint colleagues, put together this great blog post on the steps required for upgrading SharePoint and Workflow Manager together. https://joshroark.com/upgrading-sharepoint-and-wfm-at-the-same-time/
I'll also include here the Project Server upgrade document links - as Josh's blog post concentrates on the SharePoint side of the farm.
