Hello hyeokgu1998
Yes, Rigi is one of the 5 tourist places which is free with the SDP. For completion, others are Stanserhorn, Klewenalp/Stockhütte, Stoos, and Rochers-de-Naye.
As a general saying, the Saver Day Pass is valid to inhabited places where locals live all year round. And, Rigi Kaltbad is such a place. The cable car is their only connection with the rest of the country when the cogwheel train is not in operation.
→ When travelling with e-tickets such as the SDP, you are required to carry your physical passport or official identity card of your country; your ID is being verified during the ticket check. Photo copies or pictures on smartphones are not accepted.
Kind regards,
Roland