I haven't seen any Gamblig Platform who used Telegram for Promotions, most I know is that they use Discord.
Do you have any Idea why they don't have any Telegram Communities? and why does it seem they don't use this platform for their promotions?
In discord it is much easier, you only need swipe to the right if you need to see the channel or groups instantly, and some website I think they use discord to communicate since I think is far more secure, I've heard it to someone I forgot the name. And as you can see some live stream games uses discord, that's why it is far more good than telegram, you may use discord because of its unique feature than telegram.