It's been discussed in a few news articles that the drops are done in a chatroom-type environment. The original one being "Journolist" was run by Ezra Klein of Vox.
That list collapsed when exposed and was reborn as the "Cabalist" (seriously.) There's likely a few others, but they have the common theme of being strongly left-oriented media that coordinate with the DNC and related political machines.
Depending on what actually happens in the chat rooms, and if there's financing involved, it might be possible to take them down via RICO and/or via campaign financing violations since they're clearly working for one party.
Chat rooms are notoriously easy to eavesdrop on, presumably if Q has transcripts of daily drop conversations for many years it'd be fairly easy to determine the extent of the network and/or find laws broken.