No End Gateway Spawning in version 1.16-rc1

I have been playing Minecraft Hardcore for a long while now, I went to beat the Ender Dragon and the End Gateway never spawned, I searched everywhere but nothing. I have looked at the same problem and they say to use NBTeditor or NBTexplorer for the problem but I am not experienced with that app. I would like to finish all the advancements but I can't with this glitch happening. Can someone help please?