This didn't change anything, but I did finally get an image of my screen after entering my decryption password, there are some statements about failed loading of firmware before PureOS boots. The least benign-sounding is:
[ 1.402310] i915 0000:0:02.0: firmware: failed to load i915/kbl_dmc_ver1_04. bin (-2)
Which I take it has something to do with the kabylake graphics processor, but may be completely normal for all I know? There's also a statement about failed Bluetooth firmware which I assume is normal.

Hi, any advice on getting the splash screen back by editing my grub.cfg file? It's not a huge priority at this point, but I would feel better if I could resolve this.

I changed the line to GRUB_CMDLINE_LINUX_DEFAULT="quiet" and then ran "sudo update-grub" This seems to have sped things up, boot does not seem to be hanging, but I unfortunately can't quantify this. I still don't see the splash screen for disk encryption, and decided to go back and double check my grub.cfg file. Strangely, the "splash" parameter has disappeared from the "vmlinuz" lines of the file, so that may be why. I have three "vmlinuz" lines in my grub.cfg file, under separate/nested "menuentry" commands. It looks like this:

can I just change the current line to
GRUB_CMDLINE_LINUX_DEFAULT="quiet"
What is the implication of having two "resume=" targets?
The device after "cryptdevice=" is not a UUID listed in fstab or any of the partitions/filesystem shown in the disks app, but may be an alias for the main filesystem? The first "resume=" and the "root=" are followed by what is in the "Device" field of the main filesystem in disks, while the second "resume=" (after "splash") is followed by the UUID of the swap partition.
I find this all a bit hard to follow, sorry. Here are screenshots of the partitions...

Here's the actual file{F254246}

That last may be the problem. I hadn't noticed before, but that line is truncated because it is so long, and didn't copy correctly when I looked at grub before.

updated, rebooted, and still no GUI. Confirmed that the changes are still in the file.

Below is text from my /etc/default/grub -- both lines are commented out. I will try uncommenting, updating grub and rebooting, then report.

"cat: /etc/default/grub.cfg: No such file or directory"

1. grub.cfg #
2. DO NOT EDIT THIS FILE #
3. It is automatically generated by grub-mkconfig using templates
4. from /etc/grub.d and settings from /etc/default/grub

#

Yes, I updated grub before reboot.

Found the comment in /etc/default/grub and commented it out, then updated grub. Rebooted, but still the same startup sequence. Double checked to make sure the grub default file was saved with the enable_cryptodisk statement commented out.