Set Auth.net to 'Authorize only' if there are no subscription products in the cart

auth_net_activate_auth_only.php

<?php 
// note: this would require the store settings to be set to "capture" to begin with
function wc_authorize_net_cim_credit_card_change_transaction_type_no_subs( $settings ) {
	
	if ( method_exists( 'WC_Subscriptions_Cart' , 'cart_contains_subscription' ) ) {

		if ( ! WC_Subscriptions_Cart::cart_contains_subscription() ) {
			$settings['transaction_type'] = 'authorization';
		}
	}
	return $settings;
}
add_filter( 'option_woocommerce_authorize_net_cim_credit_card_settings', 'wc_authorize_net_cim_credit_card_change_transaction_type_no_subs' );