How to enter the Null Sector?

[Doc Cross]

In particular, I can't seem how to enter the far eastern lava area I have seen on many maps. I've seen people draw very rough trails on the map of how to get through, but I end up in a cave with nothing but dead ends whenever I try to follow those directions. Is there something I'm missing? Is there just a path in the cave I'm missing somehow?
Also, is the Null zone actually worth pursuing, or was it just an excuse for 'new content' that is rather specifically just large empty areas with no resources and hostiles spawned around to mimic content? I enjoy the game, but my least favorite part is just running... and running... and running... and that seems like all the Null Sector is at first glance.

[Natjur]

The way in is locked until you have completed the right missions.

And yes this game is still 99% run from A to B (and horses/moas a buggy. They are faster, but cause more issues)

[SGT.Lucek]

Here's a map and a guide
https://steamcommunity.com/sharedfiles/filedetails/?id=3027682017