$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux bullseye/sid
Release:        12-updates
Codename:       n/a

$ apt update
Hit:1 http://ftp.de.debian.org/debian stable InRelease
Hit:2 http://ftp.de.debian.org/debian testing InRelease
Hit:3 http://ftp.de.debian.org/debian unstable InRelease
Ign:4 http://security.debian.org stable/updates InRelease
Hit:5 http://ftp.de.debian.org/debian experimental InRelease
Err:6 http://security.debian.org stable/updates Release
  404  Not Found [IP: 146.75.118.132 80]
Hit:7 http://ftp.de.debian.org/debian oldstable InRelease
Hit:8 http://ftp.de.debian.org/debian stable-updates InRelease
Reading package lists... Done
E: The repository 'http://security.debian.org stable/updates Release' does not have a Release file.
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.

$ apt-get install virtualbox
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libpulse0:amd64 : Depends: libdbus-1-3:amd64 (>= 1.9.14) but it is not installable
                   Depends: libsystemd0:amd64
 libpython3-stdlib : Breaks: libpython3-stdlib:amd64 (!= 3.9.1-1) but 3.11.4-5+b1 is to be installed
 libpython3-stdlib:amd64 : Breaks: libpython3-stdlib (!= 3.11.4-5+b1) but 3.9.1-1 is to be installed
 python3 : Conflicts: python3:amd64 but 3.11.4-5+b1 is to be installed
 python3:amd64 : Conflicts: python3 but 3.9.1-1 is to be installed
 python3-minimal : Conflicts: python3-minimal:amd64 but 3.11.4-5+b1 is to be installed
 python3-minimal:amd64 : Conflicts: python3-minimal but 3.9.1-1 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

$ apt-get install python3
...

$ apt-get install virtualbox
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libpulse0:amd64 : Depends: libdbus-1-3:amd64 (>= 1.9.14) but it is not installable
                   Depends: libsystemd0:amd64
E: Unable to correct problems, you have held broken packages.

$ apt install libdbus-1-3
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  gir1.2-ayatanaappindicator3-0.1 python3.9 python3.9-minimal
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  dbus dbus-bin dbus-daemon dbus-session-bus-common dbus-system-bus-common dbus-x11
The following NEW packages will be installed:
  dbus-bin dbus-daemon dbus-session-bus-common dbus-system-bus-common
The following packages will be upgraded:
  dbus dbus-x11 libdbus-1-3
3 upgraded, 4 newly installed, 0 to remove and 891 not upgraded.
Need to get 857 kB of archives.
After this operation, 367 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://ftp.de.debian.org/debian testing/main i386 dbus-x11 i386 1.14.8-2 [90.7 kB]
Get:2 http://ftp.de.debian.org/debian testing/main i386 libdbus-1-3 i386 1.14.8-2 [214 kB]
Get:3 http://ftp.de.debian.org/debian testing/main i386 dbus i386 1.14.8-2 [98.7 kB]
Get:4 http://ftp.de.debian.org/debian testing/main i386 dbus-bin i386 1.14.8-2 [105 kB]
Get:5 http://ftp.de.debian.org/debian testing/main i386 dbus-session-bus-common all 1.14.8-2 [77.4 kB]
Get:6 http://ftp.de.debian.org/debian testing/main i386 dbus-daemon i386 1.14.8-2 [193 kB]
Get:7 http://ftp.de.debian.org/debian testing/main i386 dbus-system-bus-common all 1.14.8-2 [78.5 kB]
Fetched 857 kB in 1s (1,001 kB/s)
(Reading database ... 64254 files and directories currently installed.)
Preparing to unpack .../0-dbus-x11_1.14.8-2_i386.deb ...
Unpacking dbus-x11 (1.14.8-2) over (1.12.20-1) ...
Preparing to unpack .../1-libdbus-1-3_1.14.8-2_i386.deb ...
Unpacking libdbus-1-3:i386 (1.14.8-2) over (1.12.20-1) ...
Preparing to unpack .../2-dbus_1.14.8-2_i386.deb ...
Unpacking dbus (1.14.8-2) over (1.12.20-1) ...
Selecting previously unselected package dbus-bin.
Preparing to unpack .../3-dbus-bin_1.14.8-2_i386.deb ...
Unpacking dbus-bin (1.14.8-2) ...
Selecting previously unselected package dbus-session-bus-common.
Preparing to unpack .../4-dbus-session-bus-common_1.14.8-2_all.deb ...
Unpacking dbus-session-bus-common (1.14.8-2) ...
Selecting previously unselected package dbus-daemon.
Preparing to unpack .../5-dbus-daemon_1.14.8-2_i386.deb ...
Unpacking dbus-daemon (1.14.8-2) ...
Selecting previously unselected package dbus-system-bus-common.
Preparing to unpack .../6-dbus-system-bus-common_1.14.8-2_all.deb ...
Unpacking dbus-system-bus-common (1.14.8-2) ...
Setting up libdbus-1-3:i386 (1.14.8-2) ...
Setting up dbus-session-bus-common (1.14.8-2) ...
Setting up dbus-system-bus-common (1.14.8-2) ...
Setting up dbus-bin (1.14.8-2) ...
Setting up dbus-daemon (1.14.8-2) ...
Setting up dbus (1.14.8-2) ...
invoke-rc.d: could not determine current runlevel
Setting up dbus-x11 (1.14.8-2) ...
Processing triggers for man-db (2.9.3-2) ...
Processing triggers for libc-bin (2.37-7) ...
Running prelink, please wait...

$ apt-get install virtualbox
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libpulse0:amd64 : Depends: libdbus-1-3:amd64 (>= 1.9.14) but it is not installable
                   Depends: libsystemd0:amd64
E: Unable to correct problems, you have held broken packages.