won't display LUKS unencrypt box when running kernel 4.15.0-58 or higher.

[cowlitzron]

I have an install of Lubuntu 18.04 Bionic with a LUKS encrypted LVM. This works fine when running kernel 4.15.0-54. But, when running the latest 4.15 at this time which is 4.15.0-58, the unencrypt box fails to appear and it boots to a busybox prompt. I tried installing the latest kernel 5.0 and I have the same problem. I have to keep kernel 4.15.0-54 around even though it doesn't have the latest security update.

[cowlitzron]

An error message I got when I booted into recovery mode with kernel 4.15.0-58 is

Gave up waiting for root file system device. Common problems:
- Boot args (cat /proc/cmdline}
- Check rootdelay= (did the system wait long enough?)
- Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/mapper/ubu-root does not exist. Dropping to a shell!

[cowlitzron]

I didn't have lvm2 and some of its dependencies installed. I had uninstalled the lvm2 packages earlier not realizing they were needed to detect lvms in new kernels. I reinstalled lvm2 and needed dependencies then in a terminal typed in a root shell: update-initramfs -c -k all . I can now unencrypt the lvm using any kernel.