lightning transactions were implemented for privacy
I don't think that is why bisq implemented it, I think it is a side effect
the classic darknet markets are selling goods for monero
Many of the same goods sold on other DNMs are also sold on bisq and robosats. Namely, gift cards and cash parcels. The most popular item on silk road 2.0 was Tesco vouchers, not drugs
they are not exchanging fiat to bitcoin
Cash parcels are among the most common things I see on DNMs and that is a form of converting fiat to bitcoin and vice versa
Offers to do crypto swaps are also super common on DNMs