Copy your HTML/Post file into "Posts" and make sure to set the "CopyToOutputDirectory" in the csproj file or via tooling.
Run the ManualTest "Append_Links_And_Save_Html_Document_For_All_Posts" and hope for a success. C'est la vie.
Now you will find the your copied HTML/Post file inside the bin/debug/net6/AnchoredPosts directory with appended anchors for each link in that copied HTML/Post file.