Your PHP installation appears to be missing the MySQL extension which is required by WordPress.
Please check that the mysqli PHP extension is installed and enabled.
If you are unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress support forums.
Other Information
(other information and details relevant to your question)
Given the timing, I suspect that the MySQL extension issue may have been caused by the upgrade to PHP 8.3 we did recently. That issue should be resolved now.