CMB2 on Genesis Archive Settings.

functions.php

<?php

add_action( 'cmb2_admin_init', 'yourprefix_register_demo_metabox' );
/**
 * Creating a metabox for a Genesis CPT Archive Settings page, where the CPT is 'webinars'.
 */
function yourprefix_register_demo_metabox() {

	/**
	 * Sample metabox to demonstrate each field type included
	 */
	$cmb_demo = new_cmb2_box( array(
		'id'           => 'genesis-cpt-archive-settings-webinars-metabox',
		'name'       => __( 'Test Text', 'cmb2' ),
		'hookup'     => false,
		'cmb_styles' => true,
		'show_on'    => array(
			'key'   => 'options-page',
			'value' => 'genesis-cpt-archive-webinars',
		),
	) );

	$cmb_demo->add_field( array(
		'name'       => __( 'Test Text', 'cmb2' ),
		'desc'       => __( 'field description (optional)', 'cmb2' ),
		'id'         => 'genesis-cpt-archive-settings-webinars[test_text]',
		'type'       => 'text',
	) );
}

/**
 * Hook in to the Genesis CPT Archive Settings form for 'webinars'.
 */
add_action( 'webinars_page_genesis-cpt-archive-webinars_settings_page_boxes', function() {
	
	$cmb = cmb2_get_metabox( 'genesis-cpt-archive-settings-webinars-metabox', 0, 'options-page' );
	
	$cmb->show_form();
} );

Justin, the last thing to iron out is populating the field after the data is saved to the options table. I can retrieve the option using

$options = get_option( 'genesis-cpt-archive-settings-webinars');
$test_text = $options['test_text'];

But the value is not populated in the CMB2 field; it remains empty after the page refreshes. See https://cl.ly/1J202h101f3x