Telegram for iOS has removed the direct shortcut to a channel’s discussion group following the introduction of direct messaging to channels. The button, which previously opened the linked discussion group, now initiates a direct message chat with the channel instead. It is unclear if this change is intentional or a bug.

For channels that have enabled discussions, users can still access the group by opening any channel post, viewing its comments, and then long-pressing the “Back” button to select the group from the list that appears.This change was first noticed in version 11.12. 

source: Telegram Info Channel

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