Is getting to MT. Rigi still free with Swiss travel pass?

When are you going? The current pass fully covers travel on Mt. Rigi, both the train from Vitznau and the cablecar from Weggis up to Rigi Kaltbad. You can see the validity on the map:
https://www.sbb.ch/content/dam/sbb/de/infotexte/uebersichtskarte-sts.pdf.sbbdownload.pdf

However, I assume you are going in 2021, and they sometimes make changes to the validity with a new year. So you really need to check back later, like March, to see.

Hoping to go in June. Will check in the spring. Thanks.

Last year, the SBB website made the changes to the website regarding what the travel pass covers the first week of January. So, you'll know early on what mountains are covered. I'm hoping they add the Schilthorn back for 2021.

When we were there December 2019, the Swiss Travel Pass covered the train to Luzern, the boat ride [1 hour] from Luzern to the base of the mountain, [Vitznau,] and the cogwheel train to the top of Mt Rigi. It was beyond beautiful!

[We didn't use the cable car route.] The super-organized Swiss have the cogwheel train arrival/departures coordinated with the ferry boat.
Mt. Pilatus is not covered, but may offer a discount with the Pass.
Have a great- and safe- trip!

Just wanted to let you know that the SBB website (the Swiss railway company) has not yet updated their website with 2021 price and discount info. I have been checking for you and will post here once the updates are made.

Yes, Mt. Rigi is still fully covered by a Swiss Travel Pass. See their 2021 brochure and note that it no longer indicates the discounted services with dotted lines!