The plan is the remove support TFS 2017 and 2018. We have no possibility to test this and is cluttering the code base. This is getting harder to manage.

With older version VSTeam can still be used or by setting the VSTeam API manually or using Invoke-VSTeamRequest.

It's not set yet when this will happen (few months probably). I will add a warning message with the next release that will be shown when the module is loaded.