In the Lightning Conference 2019, Jameson Lopp mentioned that Exchanges are responsible for most of the bitcoin transactions. It is discussed in a tweet thread.
Bitcoin is not used much in darknet markets now because people realized privacy isn’t the priority for many users and Bitcoin developers. Still, we can look at the relevant charts and see that most of the source and destination associated with DNMs are exchanges or mixing services.
There is volume and few other charts for LN, Bisq, Coinjoin implementations etc on https://bitcoinkpis.com/ however its difficult to know percentage of transactions and fees from this data.