As of WP 5.5 meta boxes with alternative contexts (after_title, etc.) are not displayed correctly.

Possibly related to the addition of keyboard controls to order meta boxes.

>=WP 5.5
Classic Editor
CMB2 (develop branch)

add_action( 'cmb2_admin_init', 'cmb2_sample_metaboxes' );

function cmb2_sample_metaboxes() {

	$cmb = new_cmb2_box(
		array(
			'id'           => 'test_metabox',
			'title'        => __( 'Test Metabox', 'cmb2' ),
			'object_types' => array( 'page' ),
			'context'      => 'after_title',
			'priority'     => 'high',
			'show_names'   => true,

		)
	);

	$cmb->add_field(
		array(
			'name'       => __( 'Test Text', 'cmb2' ),
			'desc'       => __( 'field description (optional)', 'cmb2' ),
			'id'         => 'yourprefix_text',
			'type'       => 'text',
			'show_on_cb' => 'cmb2_hide_if_no_cats',

		)
    );
}