I use the LibremKey to decrypt my main drive on boot, followed these instructions to set that up. Currently I’m in that group that can’t log into their computer anymore due to updates (see here). Anyway, before I try to fix it I wanted to ensure that I have a backup of my most recent files, so I loaded PureOS on a USB drive and booted into it. However I somehow cannot figure out how I mount the LUKS encrypted main drive with the GPG key stored on the Librem Key? Any help would be greatly appreciated 
Thanks!
Still interested in this, however, I was able to unlock my LUKS drive with the passphrase that was set before I set up the unlock with the librem key. This is the same passphrase that you’ll need to boot into the recovery shell.
What exact series of steps did you do to fix this problem? Please provide that information for the sake of others. @kieran or some other more knowledgeable member may be able to help you properly document how this problem of yours was fixed.
There’s really not a fix to a problem because turns out, the problem in the first place was simply stupidity on my part. When I set my hard drive up to be decryptable with my Librem Key, the script that Purism provides is setting in up in that fashion in addition. However, you can still decrypt your drive with your previous passphrase. That is what I did in the end.
Also if I understand it correctly (and I’m surely not understanding it fully): When you set up the decryption with your librem key you are encrypting a file with the public GPG key, the secret of which you store on the Librem key. That file is your key file for decrypting your LUKS partition. When you boot up your computer and are queried to enter the PIN, you are only decrypting that file, that file then is the key to decrypting LUKS.
I’m still not clear on where that file gets stored, so more reading to do. Also: if this picture is wrong, please correct me! I’ll write something up once I figured it all out for myself first.
Okay, I can understand where you messed up, I was just reading the documentation section on using your Librem key for decryption and accessing your hard drive. I tend to absorb information fast and then slow down and ponder through it into more simple steps later on.
Thanks for clarifying your situation. We learn best from our mistakes.