Azure Pipelines: error occurred while loading the YAML build pipeline: wrong number of segments
It turns out this error message indicates the VERSION of the extension was wrong. I have to nominate the message for least helpful ever...
The GitVersion task has (finally!) released version 4 and in the Azure Pipeline world, that apparently means that v3 is deprecated. Thus, new teams who install that task extension now only have v4 available (although the team where I copied the yaml from still has v3).
The solution was to change the first step to:
steps:- task: gittools.gitversion.gitversion-task.GitVersion@4 displayName: GitVersion