I put together a quick bash script that scrapes the output of ldd in an MSYS2 environment. Running it gave me the attached list of 56 mingw64 DLLs.

After copying those DLLs from c:\msys64\mingw64\bin\ to the bin directory of the "no-deps" Emacs install folder, C-u C-x = is reporting Harfbuzz is in use. That seems to have solved my problem.

On Tue, Aug 18, 2020 at 1:56 AM <phillip.lord@russet.org.uk> wrote:

On 2020-08-18 05:55, Eli Zaretskii wrote:
>> From: Jonathan Mitchell <kyle@jonathanmitchell.org>
>> Date: Mon, 17 Aug 2020 21:05:24 -0500
>> Cc: Tak Kunihiro <homeros.misasa@gmail.com>,
>> tkk@misasa.okayama-u.ac.jp,
>> Emacs Devel <emacs-devel@gnu.org>
>>
>> I tested the emacs-27.1-x86_64.zip and .exe installer and both worked
>> fine except that C-u C-x = on any text
>> showed the font backend as uniscribe and not harfbuzz.
>
> Thanks. Can you use the dependency walker or similar tool to see if
> all the dependencies of libhafbuzz-0.dll are present in the same
> directory as libhafbuzz-0.dll itself?

I really need something to test the windows binaries in a more
systematic fashion, so we can at least test all of the dependencies in a
running Emacs.

Phil