Fixing NTFS/exFAT Superblock Mount Errors on Pop!_OS
If you're plugging an external USB HDD (like a WD Elements) into Pop!_OS and getting the dreaded wrong fs type, bad option, bad superblock error, don't panic. This usually happens for one of two reasons: either the drive wasn't safely ejected from Windows (leaving a 'dirty bit'), or your system is missing the necessary exFAT drivers.
Fix 1: Clearing the Dirty Flag (NTFS)
If your drive is formatted as NTFS and you pulled it out of a Windows machine without safely ejecting it, a "dirty flag" is set. You can use ntfsfix in the terminal to clear it.
sudo ntfsfix /dev/sdb1
(Make sure to replace sdb1 with the actual partition of your drive.)
Fix 2: Installing Missing Drivers (exFAT)
If your drive is formatted as exFAT and Pop!_OS doesn't mount it, you probably just need the exFAT drivers installed.
sudo apt install exfat-fuse exfat-utils
After running either of these fixes depending on your file system, unplug and replug the drive, and it should mount correctly.