What is the new procedure for deploying a VSTO solution via Windows Installer for Office 2016 and higher?

Question

Briefly, this procedure is no longer valid. It is possible to generate the VSTO output, manifest, DLL, etc. in the proper install directory and create registry entries (either for HKEY_CURRENT_USER or HKEY_LOCAL_MACHINE with the |vstolocal pipe), but the VSTO solution no longer installs automatically, as it did in previous versions of Office. Clearly, something has changed that isn't reflected in Microsoft's documentation.

To be clear, the VSTO file may be run directly from the program files directory, and it cleanly installs with add-ins surfaced in the Office interface, but this no longer happens automatically, regardless of this manifest entry in the registry:

file:///C:\Program Files (x86)\Company\MSProjectAddin\ProjectAddin.vsto|vstolocal

Word has it that Visual Studio support for Office is declining and possibly being phased out. Is this part of that effort, or does Microsoft intend on continuing to support customization of their Office products?