I’ve added functionality to upload profile picture by following THIS guide.
I can’t find an online guide or any documentation about WP hooks.. How to replace Gravatar profile pictures (in comment section) with custom uploaded images?
I don’t want to force my users to register Gravatar in order to change their profile picture on my site.
If you are set your custom or uploaded profile picture and need to see on front end, you can use below function .
<?php echo get_avatar( $id_or_email, $size, $default, $alt, $args ); ?>
If you have to change your gravatar to custom profile picture you can refer below link :
http://www.wpbeginner.com/wp-tutorials/how-to-change-the-default-gravatar-on-wordpress/