To check if GD & FreeType was installed, I made a simple php file. It was named info.php and I put it at the top level directory of my web page. If I remember correctly, the entire file consisted of:
<?php phpinfo(); ?>
When you go to that file (example: https://yoursite.com/info.php) it will display configuration information. I searched for GD and found that FreeType was also listed. I deleted the file afterwards since it gives information that I wouldn’t want the general public to be able to see.
I’m no expert and know nothing about GD or FreeType, but seeing them listed gave me confidence that they were installed for me. And sure enough, they were!
