Hello Hidalgo,
You can use SAP Netweaver Single Sign-On 2.0 product in order to configure SNC in OS/400 servers. You can find the availability of this product in SAP PAM (https://service.sap.com/pam) and also in the product guide (https://help.sap.com/nwsso).
The same product also allows the Client setup in Windows and MAC OS.
I hope this helps.
Best Regards,
Guilherme de Oliveira
SAP Active Global Support