Kernel panic boot error with kernel 6.5.0.21

[atactic]

Booting on kernel 6.5.0.21-generic returns error:

'Unable to mount root fs on unknown-block(0.0)'

The system starts up correctly with the previous kernel 6.7.0.17-generic

Trying fixing 6.5.0.21-generic does not work:

$ update-initramfs -u -k 6.5.0.21-generic
update-initramfs: Generating /boot/initrd.img-6.5.0.21-generic
touch: cannot touch '/boot/initrd.img-6.5.0.21-generic.new': Permission denied
W: Kernel configuration /boot/config-6.5.0.21-generic is missing, cannot check for zstd compression support (CONFIG_RD_ZSTD)
W: missing /lib/modules/6.5.0.21-generic
W: Ensure all necessary drivers are built into the linux image!
depmod: ERROR: could not open directory /lib/modules/6.5.0.21-generic: No such file or directory
depmod: FATAL: could not search modules: No such file or directory
cat: /var/tmp/mkinitramfs_uR0VlQ/lib/modules/6.5.0.21-generic/modules.builtin: No such file or directory
W: Can't find modules.builtin.modinfo (for locating built-in drivers' firmware, supported in Linux >=5.2)
/dev/mapper/control: open failed: Permission denied
Failure to communicate with kernel device-mapper driver.
Incompatible libdevmapper 1.02.185 (2022-05-18) and kernel driver (unknown version).
Command failed.
/dev/mapper/control: open failed: Permission denied
Failure to communicate with kernel device-mapper driver.
Incompatible libdevmapper 1.02.185 (2022-05-18) and kernel driver (unknown version).
Command failed.
/dev/mapper/control: open failed: Permission denied
Failure to communicate with kernel device-mapper driver.
Incompatible libdevmapper 1.02.185 (2022-05-18) and kernel driver (unknown version).
Command failed.
/dev/mapper/control: open failed: Permission denied
Failure to communicate with kernel device-mapper driver.
Incompatible libdevmapper 1.02.185 (2022-05-18) and kernel driver (unknown version).
Command failed.
I: The initramfs will attempt to resume from /dev/dm-2
I: (UUID=ae16e50c-6748-4c2f-877f-b084acd65a51)
I: Set the RESUME variable to override this.
cp: cannot access '/etc/lvm/backup': Permission denied
depmod: WARNING: could not open modules.order at /var/tmp/mkinitramfs_uR0VlQ/lib/modules/6.5.0.21-generic: No such file or directory
depmod: WARNING: could not open modules.builtin at /var/tmp/mkinitramfs_uR0VlQ/lib/modules/6.5.0.21-generic: No such file or directory
depmod: WARNING: could not open modules.builtin.modinfo at /var/tmp/mkinitramfs_uR0VlQ/lib/modules/6.5.0.21-generic: No such file or directory
/usr/sbin/mkinitramfs: 539: cannot create /boot/initrd.img-6.5.0.21-generic.new: Permission denied
update-initramfs: failed for /boot/initrd.img-6.5.0.21-generic with 2.

[atactic (atactic)]

Could restore a working Kernel 6.5.0.21 with
$ sudo apt update
$ sudo apt upgrade

However, the system starts up directly without asking for the user login, which is really weird.

There is also a security warning when updating:

$ sudo apt update
Hit:1 http://archive.ubuntu.com/ubuntu mantic InRelease
Hit:2 http://archive.ubuntu.com/ubuntu mantic-updates InRelease
Hit:3 http://archive.ubuntu.com/ubuntu mantic-backports InRelease
Hit:4 http://security.ubuntu.com/ubuntu mantic-security InRelease
Ign:5 http://linux.dropbox.com/ubuntu mantic InRelease
Hit:6 http://linux.dropbox.com/ubuntu mantic Release
Get:7 http://linux.dropbox.com/ubuntu mantic Release.gpg [488 B]
Ign:7 http://linux.dropbox.com/ubuntu mantic Release.gpg
Hit:8 https://dl.google.com/linux/chrome/deb stable InRelease
Reading package lists... Done
W: GPG error: http://linux.dropbox.com/ubuntu mantic Release: The following signatures were invalid: BADSIG FC918B335044912E Dropbox Automatic Signing Key <email address hidden>
E: The repository 'http://linux.dropbox.com/ubuntu mantic Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://dl.google.com/linux/chrome/deb stable InRelease' doesn't support architecture 'i386'