Packagemanager is corrupted

Everytime when I try to update my OS it returns these error messages:;

patrick@Lappy:~$ LANG=ENG
patrick@Lappy:~$ sudo aptitude upgrade
[sudo] password for patrick: 
Warning: Invalid locale (please review locale settings, this might lead to problems later):
  locale::facet::_S_create_c_locale name not valid
The following partially installed packages will be configured:
  initramfs-tools linux-firmware linux-image-5.11.0-41-generic 
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.
perl: warning: Setting locale failed.    
perl: warning: Please check that your locale settings:
        LANGUAGE = "en_US:nl",
        LC_ALL = (unset),
        LANG = "ENG"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
Setting up initramfs-tools (0.136ubuntu6.6) ...
update-initramfs: deferring update (trigger activated)
Setting up linux-firmware (1.187.25) ...
update-initramfs: Generating /boot/initrd.img-5.11.0-41-generic
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-5.11.0-41-generic with 1.
dpkg: error processing package linux-firmware (--configure):
 installed linux-firmware package post-installation script subprocess returned error exit status 1
Setting up linux-image-5.11.0-41-generic (5.11.0-41.45~20.04.1) ...
Processing triggers for initramfs-tools (0.136ubuntu6.6) ...
update-initramfs: Generating /boot/initrd.img-5.11.0-41-generic
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-5.11.0-41-generic with 1.
dpkg: error processing package initramfs-tools (--configure):
 installed initramfs-tools package post-installation script subprocess returned error exit status 1
Processing triggers for linux-image-5.11.0-41-generic (5.11.0-41.45~20.04.1) ...
/etc/kernel/postinst.d/dkms:
 * dkms: running auto installation service for kernel 5.11.0-41-generic
   ...done.
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-5.11.0-41-generic
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-5.11.0-41-generic with 1.
run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
dpkg: error processing package linux-image-5.11.0-41-generic (--configure):
 installed linux-image-5.11.0-41-generic package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 linux-firmware
 initramfs-tools
 linux-image-5.11.0-41-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)
Setting up initramfs-tools (0.136ubuntu6.6) ...
update-initramfs: deferring update (trigger activated)
Setting up linux-firmware (1.187.25) ...
update-initramfs: Generating /boot/initrd.img-5.11.0-41-generic
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-5.11.0-41-generic with 1.
dpkg: error processing package linux-firmware (--configure):
 installed linux-firmware package post-installation script subprocess returned error exit status 1
Setting up linux-image-5.11.0-41-generic (5.11.0-41.45~20.04.1) ...
Processing triggers for initramfs-tools (0.136ubuntu6.6) ...
update-initramfs: Generating /boot/initrd.img-5.11.0-41-generic
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-5.11.0-41-generic with 1.
dpkg: error processing package initramfs-tools (--configure):
 installed initramfs-tools package post-installation script subprocess returned error exit status 1
Processing triggers for linux-image-5.11.0-41-generic (5.11.0-41.45~20.04.1) ...
/etc/kernel/postinst.d/dkms:
 * dkms: running auto installation service for kernel 5.11.0-41-generic
   ...done.
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-5.11.0-41-generic
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-5.11.0-41-generic with 1.
run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
dpkg: error processing package linux-image-5.11.0-41-generic (--configure):
 installed linux-image-5.11.0-41-generic package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 linux-firmware
 initramfs-tools
 linux-image-5.11.0-41-generic

So there is something with Plymouth and

linux-firmware installed linux-firmware package post-installation script subprocess returned error exit status 1

initramfs-tools installed initramfs-tools package post-installation script subprocess returned error exit status 1

linux-image-5.11.0-41-generic installed linux-image-5.11.0-41-generic package post-installation script subprocess returned error exit status 1

Is there anyway to repair this, or should I make a list of my installed software and reinstall everything. I would be not to happy to reinstall because my laptop charger is broken, so I have to work on battery and have to charge with a freaking mobile charger through the USB3 port, so that would take days.

I already tried this:
sudo dpkg --configure -a
sudo apt update
sudo apt upgrade
but obviously that didn't work! ( If it did I would not ask this fine community for help. )

Can anybody help me find a cure for this problem, or do I really have to reinstall ( so shortly before a new LTS is released )? I run:
Operating System: Kubuntu 20.04
KDE Plasma Version: 5.18.7
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.11.0-41-generic
OS Type: 64-bit
Processors: 8 × Intel® Core™ i7-10510U CPU @ 1.80GHz
Memory: 15,3 GiB
On HP Envy i7 CE000ns in tripleboot with Mint 20.2 Uma and Win10 ( seperated OS's and /home partitions, swap partition and win10 and 'my documents'partition ).

Thanks in advanvance for sharing your time and knowledge. I really appreciate it.

edit 220112 at 22.04h local spanish time although my system is set to english\american, the output in the terminal is in dutch. See screenshot:. How can I change this? So I can edit the question.