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?
If it's about communication most of the gambling sites already have a chat board of their own and they have a very active discussion thread telegram is very popular on Cryptocurrency but there are also a lot of scammers and spammers here in the telegram, the admin of the telegram channel will not want to see a user bearing the name of the coin he is promoting, because some bounty hunters are using he name of the project they promote as part of bounty campaign.