I followed this tutorial which actually referred to this but after I did the installation for my CentOS 7 and went to System Settings -> Re-Check Config at VirtualMin, I see the same PHP versions I already have as shown below.
The following PHP versions are available : 5.4.16 (/bin/php-cgi), 7.0.27 (/opt/rh/rh-php70/root/usr/bin/php-cgi), 7.1.30 (/opt/rh/rh-php71/root/usr/bin/php-cgi), 5.4 (mod_php)
The following PHP-FPM versions are available on this system : 5.4.16 (php-fpm) 7.0.27 (rh-php70-php-fpm) 7.1.30 (rh-php71-php-fpm)
No PHP 7.4 is listed. Am I missing something?