I have created a WordPress shortcode (using the Code Snippets plugin) that works fine.

I need it to work within a template so, on my local system, I have edited post-content.php and inserted
$content .= do_shortcode('...');
and that works fine.

I now want to move this to a public server where I do not have permission to edit WordPress template php files.

How can I get the shortcode evaluated within a template if I cannot edit the php files (but I can add code for filters etc)?

I have managed to find solutions to all the other complex things I need to do by using php functions and filters. I have searched for solutions to this issue but the only ones I can find are about editing template files.