Only Payapal at checkout

functions.php

<?php


/**
 * Leave only Paypal, if there is a product with subscription on cart
 */
function ywsbs_only_paypal_for_subscriptions( $gateways ) {
	if ( yith_added_product_as_subscription_on_cart() ) {
		foreach ( $gateways as $k => $gateway ) {
			if ( false === strpos( $gateway, 'WC_Gateway_Paypal' ) ) {
				unset( $gateways[ $k ] );
			}
		}
	}

	return $gateways;
}

add_filter( 'woocommerce_payment_gateways', 'ywsbs_only_paypal_for_subscriptions' );

/**
 * Checks if there is a product with subscription on cart
 */
function yith_added_product_as_subscription_on_cart() {
	if ( ! class_exists( 'YITH_WC_Subscription' ) || empty( WC()->cart ) ) {
		return false;
	}

	foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
		$_product = apply_filters( 'woocommerce_cart_item_product', $cart_item['data'], $cart_item, $cart_item_key );

		if ( $_product && YITH_WC_Subscription()->is_subscription( $_product ) ) {
			return true;
		}
	}

	return false;
}