cURL error 60 when trying to use Composer

Question

In my efforts to begin developing with cakePHP, I've got to the stage of installing dependencies for Composer on my 64-bit Windows 11 system, but when I run composer diagnose on the command line, it stubbornly tells me of a failure in SSL certificate verification, despite my attempts to configure OpenSSL and the CA bundle correctly (see FAIL below).

FAIL
Checking http connectivity to packagist: OK
[Composer\Downloader\TransportException] curl error 60 while downloading https://repo.packagist.org/packages.json: SSL certificate problem: unable to get local issuer certificate

According to the error, the http connectivity to packagist is fine. But the https connectivity falls over.

I've currently got the following installed:

• php 8.1.14
• Composer 2.8.5
• OpenSSL 3.4.0.
• cURL 8.6.0.

All the dependencies that I can find are in place according to the needs of the php.ini file and the path and other system variables.

I've been troubleshooting this without success for days now!

Querying cURL's version (curl -V) returns this information:

curl 8.6.0 (x86_64-w64-mingw32) libcurl/8.6.0 LibreSSL/3.8.2 zlib/1.3.1 brotli/1.1.0 zstd/1.5.5 WinIDN libpsl/0.21.5 libssh2/1.11.0 nghttp2/1.59.0 ngtcp2/1.3.0 nghttp3/1.2.0

Is the fact that cURL is pointing to libreSSL by default instead of OpenSSL an issue ... and if so, how can I make it point to OpenSSL instead?

After some false starts, I've managed to remove all mcafee virus protection etc. from my machine. When I disable Norton 360 (my preferred online protection software) for a minute to run composer diagnose it makes no difference to the above result.

I'm not running any proxies or vpns or anything like that.

Does anyone have any ideas about how to deal with this stubborn cURL error 60?