In my experience, from 3 multi-state road trips in the 6 months I have had my Model 3, there have been 8 SCs at which I was not charged. Some of them are at hotels, restaurants, etc. I was and am rather surprised by this & I'd like to know which ones are being paid for by some host, as I'd like to thank them.
I can report that the SCs in the following list are/were NOT free to me. St. George UT, Beaver UT, Nephi UT, SLC UT, Las Vegas NV South Strip, Tonopah NV, Flagstaff AZ, Holbrook AZ, Gallup NM. I did get some free L2 charging on each of these 3 road trips, and that helped me avoid a couple of SC stops.
As an off-topic side note, I, too, wish there was CHAdeMO support for the Model 3, as I also know of at least two free CHAdeMO chargers to which I have access at places I go. As a further side note, I also wish that Tesla would finally install the SC at Kayenta, AZ, which has been "planned for this year" for the last several years.