Drupal 8.x

Using XAMPP (with PHP 8.2.12) on Windows 11, and running the installation of Drupal 8.98, there are two pages of Deprecated function warnings, followed by a fatal error:

Fatal error: Declaration of Doctrine\Common\Reflection\StaticReflectionClass::getConstants() must be compatible with ReflectionClass::getConstants(?int $filter = null): array in C:\xampp\htdocs\drupal8.local\vendor\doctrine\common\lib\Doctrine\Common\Reflection\StaticReflectionClass.php on line 109

Drupal 7 installs okay.

How do I resolve these errors, please?

I use the module mail notify. The module sends all marked nodes as an update via email at a specified time, e.g. once a week. However, I would like to be able to send certain new or updated nodes immediately via email. There are some modules for content notification, but I haven't found one for this case yet or have I missed something?

I am trying to upgrade an old 8.x site to 9.x and then 10.x.  It was originally installed via composer about 5 years ago.

The site is on Drupal 8.9.20 at the moment.  I have Composer 2.3.5, PHP 7.4.x, Apache 2.4.x, MySQL 5.7.x installed.  (I'm aware that these aren't supported any more.  I upgraded the OS and PHP went to 8.1.x and then the Drupal install broke.  I reverted to a VM snapshot and now I'm trying to update Drupal so it can run in newer PHP versions.  Once that is able to run in PHP 8.1 or higher, I'll update the OS, PHP, etc.)