Related:
Ask SN: What's the easiest way to sell something via LN? #10507
Why not just make a Bitcoin-powered Craigslist? #26798
There are existing crypto classifieds websites, but few users compared to e.g. Craigslist or Ebay: https://bitejo.com, https://miragesale.com, https://tukan.market, https://ghostnet.id, https://particl.io, https://mobazha.com.