this simply means: no space left on /boot device (too many old kernels there)

the /boot partition is currently per default only 256MBytes small and fills up fast, when there are no removal of old kernels.

# the error message continues like this
E: mkinitramfs failure cpio 141 pigz 28
update-initramfs: failed for /boot/initrd.img-4.19.0-16-amd64 with 1.
dpkg: error processing package initramfs-tools (--configure):
 installed initramfs-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 initramfs-tools
E: Sub-process /usr/bin/dpkg returned an error code (1)

what to do?

# tidy up /boot
su - root
apt autoremove

then try upgrade again

update-initramfs -u
update-initramfs: Generating /boot/initrd.img-4.19.0-16-amd64
W: Possible missing firmware /lib/firmware/rtl_nic/rtl8107e-2.fw for module r8169
W: Possible missing firmware /lib/firmware/rtl_nic/rtl8107e-1.fw for module r8169
W: Possible missing firmware /lib/firmware/rtl_nic/rtl8168h-2.fw for module r8169
...

update-grub2
Generating grub configuration file ...
Found background image: /usr/share/images/desktop-base/desktop-grub.png
Found linux image: /boot/vmlinuz-4.19.0-16-amd64
Found initrd image: /boot/initrd.img-4.19.0-16-amd64
Found linux image: /boot/vmlinuz-4.19.0-14-amd64
Found initrd image: /boot/initrd.img-4.19.0-14-amd64
done

# close all programs & cross fingers
reboot
admin