Get list of function names which is hooked available on particular hook.

functions.php

<?php
/**
 * Change `the_content` thing in below function with your hook in filter
 * - You can change $wp_filter to $wp_actions to get details of action hooks.
 *
 * NOTE: THIS IS FOR ONLY DEBUG PURPOSE NOT SEND THIS CODE TO PRODUCTION.
 */
function vk_list_hooks() {
	global $wp_filter;

	$functions = [];
	foreach ( $wp_filter['the_content']->callbacks as $callbacks ) {

		foreach ( $callbacks as $callback ) {

			if ( isset( $callback['function'] ) && ! empty( $callback['function'] ) ) {

				$callback_function = $callback['function'];

				if ( is_string( $callback_function ) ) {

					$functions[] = $callback_function;
				}
			}

		}
	}

	echo '$functions: <pre>';
	print_r( $functions );
	echo '</pre>';
	die;
}
add_action( 'wp', 'vk_list_hooks', 999 );