Not that I use them (I actually really don't (like that would be something anyone would believe (oh God, I am getting lost inside a parenthetical alternative universe)))...
But I keep an eye on dark net markets mostly out of curiosity. Wall Street Market was shut down this summer, but XMR was a preferred crypto there and most vendors took it. Some even had special discounts for XMR users. I saw someone who ran a cannabis gummy XMR sale regularly.
Currently the biggest DNMs are probably: Empire, Tochka, Berlusconi, Nightmare, and Cryptonia.
All of those take XMR.
I am a libertarian. But to be honest I do not think this use of XMR is what makes it important. I just think it is a natural side effect of it being one of the truly useful digital currencies. I am also one of the probably few old school crypto people who does NOT see Ross Ulbricht as a hero. I see him as a criminal (but his sentence is ridiculous). Almost all other projects are garbage at worst and well-meaning testnets at best. I am looking forward to XMR continuing to shed it's darknet reputation and being seen for the privacy preserving tour de force that it is.
That said, there is no doubt it is THE trusted privacy currency on the dark web. People probably still use Bitcoin more and are fools for it IMHO.
Without really getting into all the moral and philosophical stuff, I just want to know if XMR's use is trending at DNM's or where to get the data.