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Please keep in mind that Joomla! 3.6 was released in July 2016; eight and a half years ago. Back then the latest PHP version which had been released was PHP 7.0 (released in December 2015).

Your local server is using PHP 8.1 which was first released in November 2021.

The old software you are trying to use predates the PHP version you are using by five years. In computer terms, that's an equivalent measure of time as that between the invention of wheel and that of manned space exploration. The ancient software you are trying to use won't work on PHP 8, and it would even crash with PHP versions as low as 7.1. You'd have to use PHP 5.6.

On a similar note, your local server is probably using MySQL 8.0 or 5.7. Joomla! 3.6 predates MySQL 8 by several years. Even MySQL 5.7 was pretty new (having been released just a few months before Joomla! 3.6), meaning it's probably not fully compatible. You need a more vintage version, possibly something like 5.5.

You are now entering the realm of PHP archaeology. There are two ways to proceed.

One way is to install Windows 8.1 (or a very old Windows 10 version) on a virtual machine and install an old WAMPServer version. I would guess the last version from late 2015 would probably have the right versions of PHP and MySQL.

If you are on a Mac that's not an option. In this case, you need to use Docker to run a server environment of the right vintage. A couple of years ago I did just that: https://github.com/nikosdion/php_archaeology. The default settings are PHP 5.6, Apache 2.4, and MySQL 5.5 which is indeed what you need to restore your ancient site.