This may sound crazy, but the lock is located in Reaper's March near Willowgrove, just north of Willowgrove Cavern near a tree for some reason. That's how I managed to get in.

This may sound crazy, but the lock is located in Reaper's March near Willowgrove, just north of Willowgrove Cavern near a tree for some reason. That's how I managed to get in.
Dude you're awesome, that's exactly right!!! 😂
For anyone else, here's a screenshot of the exact location. Once you "unlock" it, you then have to go all the way back to Glenumbra and just walk in the gate (past the rest of the poor guys in the queue.. 🤣) Insane, but it works. Thanks taiyoukei! 👍

There are two hitboxes overlapping. If you hover over the door you might eventually find the right one which says „unlock“. You‘re supposed to unlock before using the door.
i get why you would think this, and it did work for me, but i think its more likely that we are just getting the unlock prompt after the last person unlocked the gate and went through. And then it disappears after the first person spamming gets it and starts to lockpick
I don't know if anyone has said this, but there is a workaround: join a group, and then it should work. Only one person can interact with the gate, and it has a 30-second timer that resets. Hopefully this helps