I don't think there's a bitcoin telegram group that is official but there are telegram groups that are formed or created for the same reason which is Bitcoin and related discussions for everyone who wants to learn about it. Nevermind about the telegram group for a moment, actually this forum would also be a good platform to learn bitcoin, miners and you could also ask if he have telegram group full of miners or whatever it is that is related to bitcoin and mining. It's been asked many times in board to but moved in mining board sooner or later so better check the board right away and we don't know you have found what you are looking for such as knowing what iminungs the best mining rigs to use depend on your budget.