I went to the Beneath and spawned in a spawner room with no teleporter to be found.
https://imgur.com/a/KD6hZF8

Version is 3.0.8

Edit: I cheated in a teleporter, went to the overworld, went back to the beneath, and the teleporter room overwrote the spawner room with a new teleporter. I assume that the zombie spawner room overwrote the majority of the teleporter room which is why it wasn't there at the beginning. https://imgur.com/a/tcvxMae