WCF service fails on IIS 10 on Server 2019

Question

I am migrating WCF services to a new 2019 server running IIS10. The server that these services come from is a IIS8.5 running on Server 2012R2. It is obvious that a IIS backup/restore might/will fail as a number of discussions will suggest. I have set up my remote deployment from VS2019 the same as for the old server. I can deploy webs and REST services without any problems - BUT WCF services fail:

Fiddler reports 404 Not Found. Calling the service via test programs under debug brings up the following:

25-02 11:09:43 [24016] FATAL bSm.Kll.Program - System.ServiceModel.ProtocolException: The remote server returned an unexpected response: (405) Method Not Allowed. ---> System.Net.WebException: The remote server returned an error: (405) Method Not Allowed. at System.Net.HttpWebRequest.GetResponse() at System.ServiceModel.Channels.HttpChannelFactory`1.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) --- End of inner exception stack trace ---

Server stack trace:
at <System.ServiceModel.Channels.HttpChannelUtilities.ValidateRequestReplyResponse(HttpWebRequest request, HttpWebResponse response, HttpChannelFactory1 factory, WebException responseException, ChannelBinding channelBinding)<br> at System.ServiceModel.Channels.HttpChannelFactory1.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)
at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

I am reasonable sure that I am missing credentials for the service, the problem is WHERE / WHAT is the additional requirement enforced by this server.

As an aside: I already ran across the problem that the Web Deployment tool has a extra requirement for a "User delegate" which was quite a hurdle on its own. The 3.6 version of the tool had to be collected from the MS website before this requirement was revealed.