I’ve just rechecked it on my test server (WooCommerce v3.5.4 and WordPress v5.0.3) – it seems to be working fine here. What issues are you having? Custom payment gateways are not shown at all? Or you can’t finish the order? Or something else?
P.S. If you wish you can create/share an admin account to your server (WP and preferably FTP), so I could log in and check what’s going on. My private email is [email protected].