Why is the Apache2 module not in the mods-available library?

I installed both PHP 5.6 and 7.4 and their apache2 modules:

$ sudo apt install php5.6 libapache2-mod-php5.6
$ sudo apt install php7.4 libapache2-mod-php7.4

However, when I try to enable php7.4, I get an error:

$ sudo a2enmod php7.4
ERROR: Module php7.4 does not exist!

Indeed, the module is not found where it should be:

$ ls -la /etc/apache2/mods-available/php*
-rw-r--r-- 1 root root 867 May 14 11:48 /etc/apache2/mods-available/php5.6.conf
-rw-r--r-- 1 root root 102 May 14 11:48 /etc/apache2/mods-available/php5.6.load

php5.6 is there, but php7.4 is not. How can I fix this?