Telegram is adopted widely by the “crypto community”. But Monero should not be apart of this, as it’s a centralized platform doing zero metadata protection and only encrypted on mobile. Here’s an excellent video you can send your friends who request you to message them on there: https://video.simplifiedprivacy.com/why-telegram-sucks/
Best place for XMR trading is AgoraDesk/LocalMonero
Right. But Agoradesk/LocalMonero uses Telegram for their customer support because they and their customers are ignorant of the concepts in this video
Localmonero uses matrix too for those who want it
Unfortunately, many cash by mail Monero sellers leave their contact info as a telegram address on their intro page. I wish they would all have to leave an protonmail email address or some other way to contact them using Tor.