Comment 11 for bug 1829805

The problem here is the installer failed to build/install initrd.img.

After installing into a LVM LV via libvirt and seeing the error I mounted the disk image contained in the LV and explored:

$ sudo losetup -f --show -P /dev/VG02/lubuntu1910
/dev/loop5
$ sudo mount /dev/loop5p1 /mnt/target
$ sudo TERM=screen chroot /mnt/target

# ls -l /boot/
total 13548
-rw-r--r-- 1 root root 224306 Jun 4 16:22 config-5.0.0-17-generic
drwxr-xr-x 5 root root 4096 Jun 18 20:50 grub
lrwxrwxrwx 1 root root 27 Jun 18 17:41 initrd.img -> initrd.img-5.0.0-17-generic
lrwxrwxrwx 1 root root 27 Jun 18 17:41 initrd.img.old -> initrd.img-5.0.0-17-generic
-rw-r--r-- 1 root root 182704 Jan 28 2016 memtest86+.bin
-rw-r--r-- 1 root root 184380 Jan 28 2016 memtest86+.elf
-rw-r--r-- 1 root root 184840 Jan 28 2016 memtest86+_multiboot.bin
-rw------- 1 root root 4378278 Jun 4 16:22 System.map-5.0.0-17-generic
lrwxrwxrwx 1 root root 24 Jun 18 17:41 vmlinuz -> vmlinuz-5.0.0-17-generic
-r--r--r-- 1 root root 8703736 Jun 18 20:50 vmlinuz-5.0.0-17-generic
lrwxrwxrwx 1 root root 24 Jun 18 17:41 vmlinuz.old -> vmlinuz-5.0.0-17-generic

Notice the symlinks from initrd.img{,.old} point to non-existent initrd.img-5.0.0-17-generic,