How do I change the salt used for the user password when creating an account? I am working on Drupal 8 site where the client has asked us to use their own custom salt when storing the user password in the database.

Is it possible to set a custom salt for a Drupal site?

The client is thinking of the feature from a security perspective. What can be done?
In site/default/settings.php  there is a config for salt

$settings['hash_salt'],  passwords are hashed with this salt. you can change it to whatever the client has asked you.