From the instructions outlined in the sample README, it looks like to leverage this registration free mechanism, one needs to create the process - app - manifest and supply the WinRT activation class mapping in there.
But, how if I don't own the process, therefore unable to create or edit the app manifest?

Here's one scenario I'm faced with:
I have a C++ DLL that is loaded as a COM component by an external process that I don't own.
And from my C++ assembly, I would like reference a WinRT component written in C# and I can't figure out how to activate the runtime classes; is there any way to accomplish this?
I attempted to create a manifest for my C++ component - with a .dll.manifest extension - but that doesn't seem to work...

Can this be done with a reg-free free mechanism?
Thanks!

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I have tried this way to invoke my cpp winrt dll from other c# assembly with a test C# exe ,but i have to let my C# exe module to depend on this cpp winrt dll and add a manifist file and add a reference of VCRTForwarders or it will cause a C# System.TypeLoadException. So can I use this invoke machanism from a standalone C# assemly ? Or I didn't use it correctly?

I built both the WinRT component and the C# sample. Clicking on the button causes this exception:

System.IO.FileNotFoundException: The specified module could not be found. (Exception from HRESULT: 0x8007007E)
at System.StubHelpers.StubHelpers.GetWinRTFactoryObject(IntPtr pCPCMD)

I'm on Windows build 18362.239.

Using Windows Runtime activation mechanism( Registration-free WinRT ), a User Control class can be exposed and loaded into the MFC application for modernizing purpose. But when using another user control of same namespace in the User Control XAML that is hosted over MFC application, it crashes immediately at startup and throwing the following exception.
‘The type 'User Control' was not found’
It is possible to access the other user control class's properties from the C++ file of main User Control, so it seems like an issue while trying to access from XAML only.
How do we can handle “The type 'User Control’ was not found.” exception in Registration-free WinRT?
Reference links :
https://blogs.windows.com/windowsdeveloper/2019/04/30/enhancing-non-packaged-desktop-apps-using-windows-runtime-components/
https://learn.microsoft.com/en-us/windows/apps/desktop/modernize/host-custom-control-with-xaml-islands-cpp