This is a PHP version mismatch. Akeeba Backup cannot do about it, it's all about Joomla! itself and the extensions you are using with it.

I think that your new server is probably using PHP 8.3 or 8.2 which is too new for Joomla! 3. The maximum version officially supported by Joomla! 3 is PHP 8.0, and there is partial support for PHP 8.1. However, most extensions made for Joomla! 3 had a support for at most PHP 7.4, or even 7.2. Try stepping down the version of PHP you are using on your server until the site works.

For what it's worth, I did too go from a Mac to a Windows machine over the weekend. My Joomla! 3 development site was unhappy with PHP 8.3. I am running it on PHP 8.1 with the note that I am only using my own extensions which I now for a fact were made to fully support PHP 8.1 (and 8.2, if I make changes to Joomla! core files so that Joomla! itself doesn't break on 8.2).