Set Default WordPress Image Editor to GD Library

functions.php

<?php

function xxx_image_editor_default_to_gd( $editors ) {
    $gd_editor = 'WP_Image_Editor_GD';
    $editors = array_diff( $editors, array( $gd_editor ) );
    array_unshift( $editors, $gd_editor );
    return $editors;
}
add_filter( 'wp_image_editors', 'xxx_image_editor_default_to_gd' );

// from https://www.wpbeginner.com/wp-tutorials/how-to-fix-the-http-image-upload-error-in-wordpress/

?>