If I open telegram and go to ‘find people nearby’ I am presented with a long list of drug dealers and prostitutes advertising their services. So they not only help with communication, they help with advertising, and since this is all public, they can’t really say they’re not aware

Those are just fake account scammers, you won't be able to buy sex or drugs from any of them. And they get banned all the time.

Do you have a source or no?

This documentary on the drug trade in Belgium has a segment on the uberisation of drug dealing and shows the usage of telegram for that purpose: https://youtu.be/9-DwggVrt2c?t=2613&si=SBct_5WUZCoJmcgA

Yes media has been saying this about telegram since it exists. Yet somehow I doubt all 900 million users are dealers/users.

I was hoping for something more substantial, that showed telegram is used and other apps aren't, for that purpose.

Aren't they saying "whatsapp" and "signal" 2 seconds after "telegram"?

Anecdotal Instagram evidence on the situation in Berlin: https://www.instagram.com/reel/CxJGJs7s-lE/

In Finland, stuff seems to be more on Telegram than on dark web as well