gnupg php extension

how do i install the gnupg php extension (for all php versions) and enable it by default for all users, all servers

You will need to install some dependencies first, (with apt) at least:

autoconf
make
g++
libgpgme-dev

Then for any given php version, run (example for PHP 8.4);

/opt/ecp-php84/bin/pecl install gnupg

Lastly add a php.ini directive for extension set to gnupg.so. You can do this globally, per server or per-website.