The Bug

If the player destroys the End Gateway block in Creative (or Survival using a giant mushroom), it will not regenerate if the player travels to that portal again.

It would be expected that the game would regenerate an end gateway if it detects it to be broken in any way (including the bedrock part).

How to Reproduce

Note: You can use your own seed for this, but I will specify the seed and coordinates in the reproducing instructions to make it easier to follow.

Make a world with the seed 8323212855974205834.

Run the command below to teleport directly to the End:

/execute in minecraft:the_end run tp @s 0 70 0

Then kill the Ender Dragon using:

/kill @e[type=minecraft:ender_dragon]

Go through the end gateway that should've generated at -96 75 -1 using an ender pearl to generate the end gateway in the outer end islands. Go back through that gateway to return to the main island.

Destroy the end gateway block. Then run the command below to teleport to the end gateway that linked to the one you just destroyed:

/tp @s -1021 60 -16

Go through that end gateway in the outer islands back to the main end island.

← Note how the end gateway has not regenerated.

Additional Notes

Related to MC-238028.