How to install JSmin php extention?

This one: GitHub - sqmk/pecl-jsmin: PHP PECL extension for JavaScript minification

Probally not supported any more or at least follow the instructions there …

If it doesn’t work good luck…

This is not the answer, the question is: Where Hestia stores extensions, cause the instructions in the description are for a generic approach (and aren’t working).

All PHP default …

There is nothing custom about it.