I don't want to make a video, but I wanted to make a note somewhere before I forget. I found a relatively easy out-of-bounds which gets below the entire world map, and it looks like it can be used to travel relatively long distances. I have not seriously examined it; I get horrible vertigo from going OOB and so I don't enjoy exploring it.

I'm playing on PS4. So, there's a spoilerriffic series of cutscenes near the recluse spider. Campfire-save before going into that area, do the rooms leading up to the recluse spider, and then during the spoilerriffic cutscenes, power off the PS4 (or likely just close the game). This creates a glitchy quicksave.

Upon loading, you'll be near the recluse spider, ready to trigger the cutscenes. Instead, try to leave the room by going back the way you came, using Triangle on the door. The door will open, and you'll be faced with an empty area that has no geometry. You can simply jump OOB here. Try gliding; you can glide out of the area and you'll get the overworld map loaded in.

I have no idea what this state can do. I just know that it appears reliable to set up and trigger, and I'm on my first playthrough so I just want to document it and continue playing.

Edit, 10mo later: Looks like Guerrilla has patched this. TBH it looks like they rewrote the entire sequence. Now, there is an autosave after each triangle, starting with the gene-locked hatch, and any restart-at-save attempt will just restart the boss fight.