i tried copying all my popOS files back to the root of the ext4 partition and was able to boot, but the permissions are all screwed up, and i can't execute anything so i'm just going to reinstall from rescueshell. i think thats the best method for now until this gets sorted out. i'm not confident its possible to have a stable linux install by just copying files in this manner, or by just extracting the file to a blank partition.
having said all that, i was never able to get anything to boot with my ps4 pro belize until i added the bootargs.txt file to the fat32 partition. i believe that's necessary and it isnt mentioned much, so definitely try adding it if you're having problems. its just a single line of text as follows:
drm.edid_firmware=edid/1920x1080.bin