Second vote for FB marketplace. Drop the price a little, and the tube steps will sell. I have sold SR5 wheels, used tires, and port-installed options that I didn’t want. Be willing to accept reasonable offers - the stuff is worth nothing just sitting in the garage.
Craigslist. I just listed mine for $300 locally and in less than 24hrs I had a buyer and made the sale.
This was only after I offered them here in the classifieds for 2 weeks at $200 and everyone was too cheap to pay to have them shipped. (shipping cost on these is a bit ridiculous)
My next shot at dumping them was going to be ebay.... where they are listed for $400-$500+ but the fees will eat you alive.