Updated the Dell XPS 15 this morning using the latest Linux 7.2.6 and mkinitcpio 42 only to be repeatedly greeted by the LUKS unlock prompt. After some quick Kagi searching, I noted this little nugget in the release notes:

• install/sd-encrypt deprecates the mkinitcpio-specific
  /etc/crypttab.initramfs file in favour of using the x-initrd.attach
  option in /etc/crypttab (in the fourth field). This matches the
  behaviour of other initramfs generators.

If you’re using crypttab.initramfs take heed! Your shit’s gonna break! (Mine did!) No amount of re-enrolling is going to fix this one.

The fix is easy enough, and documented on the Wiki here. Merge your crypttab.initramfs into /etc/crypttab and include x-initrd.attach in the 4th field like so:

/etc/crypttab

root  UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX  none  x-initrd.attach,tpm2-device=auto

Update your initrd and reboot!

Hold on to your butts….