First a note: Yes, I'm well aware this extension in deprecated and has a ton of security flaws, I'm duplicating a clients active server in docker for recovery and migration (after client's server was compromised).
Clients server is Centos6 based with php 5.6 and uses the original php mysql module (they just call it the original module) https://www.php.net/manual/en/book.mysql.php
I've tried a few of the original mysql repos (remi, webtatic) and they install PDO (the new mysql module).
I'm looking for a way to add the (insecure) original module to my docker container for working locally to recover assets and modernize the project, however it seems most of the repo's are using security best practices to remove the flawed software (or I'm not correctly understanding how to enable it).
I'm willing to build it myself if theres a repo of the original source, or if theres prebuilt somewhere I'm not aware of I'd be grateful.
Looks like you have not checked properly.
With a proper configuration, following the Wizard you can install the mysql extension, and most existing extensions:
The package name is php-mysqlnd and provides
You can check using:
Of course I recommend to switch as soon as possible to mysqli to avoid being blocked to 5.6 which have reached its end of life, even if "remi" repository have some security backports.