Wyv Hello. I had that exact same issue on my PS4. It couldn't create newroot and it would crash after the busybox logo when trying any command 3 times (think of busybox like a small distro, or something like that). But I only had that issue when installing on internal. I'm honestly shocked because I dont remember what I did and it was just a couple of weeks ago...
I then decided to use the method 2 I described instead, tho I do have it installed on the internal drive...
Sorry to ask you this question, but I need to: did you follow the guide precisely? The distro you downloaded, whichever it is, needs to be called "psxitarch.tar.gz/xz". I do still recommend you go and try the method 2. If you are on windows, you can either boot a live iso of a distro like linux mint on your pc or on a vm to format the drive in ext4 like the guide describes.
In the meantime, I'll try to recall the steps I took to install it on the internal drive (i know you did external, but the error was the same. also i think i had it the first times i tried external too). All I remember is that the files weren't in the correct place initially, but on the external drive it's unlikely.
EDIT: /dev/ newroot/ issue is, if i understand correctly, due to it not finding a linux installation on your drive...? Again, please try the second method, tomorrow I'll work with you on finding a fix for this and updating the guide, because it's one of the really important thigns i missed.
