WordPress - Unhook a class method from an action or filter, even if you don't have a reference to the class instance.

unhook_class_method.php

<?php

/**
 * Removes hooks that trigger a certain class method,
 * even if you don't have a reference to the class instance.
 *
 * @global \WP_Hook[] $wp_filter
 * @param string $filter
 * @param string $class
 * @param string $method
 * @param int $priority
 * @param int $args
 * @return int How many filters were unhooked
 */
function unhook_class_method( $filter, $class, $method, $priority = null ) {

  global $wp_filter;

  $to_remove = [];

  foreach ( $wp_filter[ $filter ]->callbacks as $hook_priority => $callbacks ) {

    if ( $priority !== null && $priority !== $hook_priority ) {
      continue;
    }

    foreach ( $callbacks as $callback ) {

      if (
        is_array( $callback[ 'function' ] ?? null ) &&
        is_object( $callback[ 'function' ][ 0 ] ?? null ) &&
        get_class( $callback[ 'function' ][ 0 ] ) === $class &&
        ( $callback[ 'function' ][ 1 ] ?? null ) === $method
      ) {
        $to_remove[] = [ $filter, $callback[ 'function' ], $hook_priority ];
      }

    }
  }

  foreach ( $to_remove as $args ) {
    call_user_func_array( 'remove_filter', $args );
  }

  return count( $to_remove );
}