$ sudo apt install -f
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  snap-confine
Use 'sudo apt autoremove' to remove it.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Setting up initramfs-tools (0.122ubuntu8.9) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.122ubuntu8.9) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-1076-raspi2
W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.
Unsupported platform.
run-parts: /etc/initramfs/post-update.d//flash-kernel exited with return code 1
dpkg: error processing package initramfs-tools (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 initramfs-tools
E: Sub-process /usr/bin/dpkg returned an error code (1)