Server IP instead of client's is shown in Apache access log for website hosted on Plesk server due to disabled "remoteip" Apache module

Applicable to:

The domain's access log in Domains > example.com > Logs > Apache access (the file is /var/www/vhosts/example.com/logs/access_log) contains server's IP address instead of client's.
rpaf Apache module is shown as enabled and the remoteip module is shown as disabled in Tools & Settings > Apache Web Server > Apache modules:
Nginx proxy mode is enabled in Domains > example.com > Apache & nginx Settings > nginx settings.
In Tools & Settings > Server Components, the version of the Apache is 2.4.x:
PHP variable $_SERVER['REMOTE_ADDR'] in the website code returns the IP address of the Plesk server instead of the actual IP address of the visitor.

Apache module remoteip is disabled.

In Plesk interface

Log into Plesk.
Go to Tools & Settings > Apache Web Server.
In the section Apache modules, disable the module rpaf, enable the module remoteip and click OK or Apply to save the changes:

In the server console

Connect to the server using SSH.
Enable remoteip Apache module:

# plesk sbin httpd_modules_ctl --enable remoteip
Disable rpaf Apache module:

# plesk sbin httpd_modules_ctl --disable rpaf
Restart Apache:
- In CentOS, RHEL, CloudLinux:
  
  # service httpd restart
- In Debian and Ubuntu:
  
  # service apache2 restart