From GameWatcher: “Borderlands 3 is out now, and the long-awaited sequel is filled to the brim with all manner of quests, characters, guns, and secrets to uncover – but some of those secrets are harder to access than others. This certainly goes for the Borderlands 3 Mouthpiece secret room in the Holy Broadcast Center, which seems impossible to access.”
Source: N4G PC Borderlands 3 Mouthpiece Secret Room – How to get inside the Holy Broadcast Center secret area