Unable to read multipart response from SOAP11 service with MTOM?

Hello, we have following SOAP answer from one of the services, running SOAP 1.1 with WS Addressing:

HTTP/1.1 200 OK
X-Backside-Transport: OK OK
Connection: Keep-Alive
Transfer-Encoding: chunked
Date: Wed, 28 Sep 2022 11:40:07 GMT
X-Powered-By: Servlet/3.1
Content-Type: multipart/related; type="application/xop+xml"; boundary="uuid:98eb4321-4665-4970-a24d-e9bc20cd051c"; start="<root.message@cxf.apache.org>"; start-info="text/xml"
Content-Language: en-US
X-Global-Transaction-ID: a38d5ad06334329744471fad

--uuid:98eb4321-4665-4970-a24d-e9bc20cd051c
Content-Type: text/xml; charset=UTF-8
Content-Transfer-Encoding: binary
Content-ID: <root.message@cxf.apache.org>

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header><wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:wsa="http://www.w3.org/2005/08/addressing">
... <rest of envelope>
--uuid:98eb4321-4665-4970-a24d-e9bc20cd051c--

According to this W3 documentation, this message is a valid SOAP 1.1 with multipart content.

The problem is, whether I want to read this message from client using MTOM encoder MtomMessageEncodingBindingElement, there is an exception telling me that Root MIME part must have media type 'application' and media subtype 'xop+xml', and this is true, because my Root part has MIME = text/xml.

This is the part of internal code throwing that exception.

https://github.com/dotnet/wcf/blob/d1a04680c77e5d47138c1763b42ab47295f5a1b3/src/System.Private.ServiceModel/src/Internals/System/Xml/XmlMtomReader.cs#L225-L227

Whole exception:

Unhandled exception. System.ServiceModel.CommunicationException: Error creating a reader for the MTOM message
 ---> System.Xml.XmlException: Root MIME part must have media type 'application' and media subtype 'xop+xml'.
   at System.Xml.XmlMtomReader.ReadRootContentTypeHeader(ContentTypeHeader header, Encoding[] expectedEncodings, String expectedType)
   at System.Xml.XmlMtomReader.Initialize(Stream stream, String contentType, XmlDictionaryReaderQuotas quotas, Int32 maxBufferSize)
   at System.Xml.XmlMtomReader.SetInput(Stream stream, Encoding[] encodings, String contentType, XmlDictionaryReaderQuotas quotas, Int32 maxBufferSize, OnXmlDictionaryReaderClose onClose)
   at System.Xml.XmlMtomReader.SetInput(Byte[] buffer, Int32 offset, Int32 count, Encoding[] encodings, String contentType, XmlDictionaryReaderQuotas quotas, Int32 maxBufferSize, OnXmlDictionaryReaderClose onClose)
   at System.Xml.XmlMtomReader.Create(Byte[] buffer, Int32 offset, Int32 count, Encoding[] encodings, String contentType, XmlDictionaryReaderQuotas quotas, Int32 maxBufferSize, OnXmlDictionaryReaderClose onClose)
   at System.ServiceModel.Channels.MtomMessageEncoder.MtomBufferedMessageData.TakeXmlReader()
   --- End of inner exception stack trace ---
   at System.Runtime.AsyncResult.End[TAsyncResult](IAsyncResult result)
   at System.ServiceModel.Channels.ServiceChannel.SendAsyncResult.End(SendAsyncResult result)
   at System.ServiceModel.Channels.ServiceChannel.EndCall(String action, Object[] outs, IAsyncResult result)
   at System.ServiceModel.Channels.ServiceChannelProxy.TaskCreator.<>c__DisplayClass1_0.<CreateGenericTask>b__0(IAsyncResult asyncResult)
--- End of stack trace from previous location ---
   at Program.<Main>$(String[] args) in C:\Users\
   at Program.<Main>(String[] args)

I am using .NET 6.0 with System.ServiceModel.Primitives 4.10.0 package.

Is there any way to get this working?

dotnet / wcf

Unable to read multipart response from SOAP11 service with MTOM? #4918