Ubuntu – Ubuntu 17.10 fails to boot with AMD graphics card

I have been running 17.04 with the amdgpu driver. After upgrading to 17.10, it boots to a deep purple (blank) screen. I have whole disk encryption, so it would normally show a password prompt at this point.

The graphics card is Radeon R9 290X.

When resetting the computer, it boots to the GRUB menu, and I've tried different options:

• Kernel 4.10.0-37 works, but stops before the boot process finishes (Starting GNOME). No graphics or login prompt.
• Kernel 4.13.0-16 in recovery mode takes me to the recovery menu.
  • Resume: Prompts for a password for my drives. It times out before I can enter all the passwords*, and it takes me back to the recovery menu. Resume again gives a blank screen. If I first drop to root shell and do systemctl start dev-mapper-pool, then enter passwords, then exit the shell and choose resume, I can get to a basic desktop with low graphics. I can log in,etc,. This is a huge improvement for me!
  • failsafeX: Boots to the oh so familiar low graphics screen, but none of the options help me.
  • root shell: This works. I can also remount read-write. I uninstalled some AMDGPU-PRO packages I had for OpenCL support, but it doesn't make a difference.

I have got this purple screen before, but it's usually fixed in a matter of uninstalling some AMD driver I've tried. Now, I can't see what to do..

*I have the same PW on all drives, and normally it only prompts once for the PW, now it asks for each drive.