Linux package conflict

The issue was caused by a package conflict during the Kali rolling upgrade. After fixing the missing Kali archive signing key, apt update was able to pull the latest package metadata, and apt full-upgrade started upgrading the system.

However, the old package python3-pyinstaller-hooks-contrib conflicted with the newer package pyinstaller-hooks-contrib because both packages tried to own the same file:

/usr/lib/python3/dist-packages/_pyinstaller_hooks_contrib/__init__.py

As a result, dpkg stopped with an overwrite error, leaving some packages only partially installed or not fully configured. This likely caused the desktop environment/X server to fail, which led to the black screen in the Proxmox console and the XRDP error saying that the X server could not be started.

The issue was resolved by forcibly removing the old conflicting package and then completing the upgrade:

sudo dpkg -r --force-depends python3-pyinstaller-hooks-contrib
sudo apt full-upgrade -y
sudo apt --fix-broken install -y

After that, the package state was clean again and the system was able to start normally.