Hi,
Unfortunately I wasn't able to find out how the new map file system works, but I'm pretty sure this is a compressed file format, wich makes sense for the maps since they are a lot larger than the other files. Maybe the devs made their own compressing format. However, I did find out that you can still download the map. You just have to replace the .glb with .nasset
If you want to download the .glb file, you should look for it on Discord. I'm pretty sure I saw someone saying they were there.
Sorry for not finding anything helpful. I will let you know if I discover anything new.