I have fought this battle for years to a point that it is almost humorous.
TN requires NRTL listing with some jurisdictions enforcing it stronger than others.
So often, the first phone calls to the supplier is "I don't know what you are talking about", or "no one requires that". Subsequent calls finally result in "Oh, you are one of THOSE! "
Often I have seen the manufacturer come to the scene, modify the equipment to meet the NRTL standard and then have a field evaluation.
As noted above in Post #7, many suppliers offer the product as "listed" or not with a price variation.
At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.