Почему я получаю неудовлетворенные ошибки зависимостей при установке драйверов Nvidia 418 в Ubuntu 18.04?

Я установил проприетарный графический PPA и успешно запустил apt update, но у меня возникают следующие ошибки при попытке установить драйверы Nvidia 418:

$ sudo apt install nvidia-driver-418
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:
 nvidia-driver-418 : Depends: libnvidia-gl-418 (= 418.56-0ubuntu0~gpu18.04.1) but it is not going to be installed
                     Depends: nvidia-utils-418 (= 418.56-0ubuntu0~gpu18.04.1) but it is not going to be installed
                     Depends: xserver-xorg-video-nvidia-418 (= 418.56-0ubuntu0~gpu18.04.1) but it is not going to be installed
                     Depends: libnvidia-cfg1-418 (= 418.56-0ubuntu0~gpu18.04.1) but it is not going to be installed
                     Depends: libnvidia-ifr1-418 (= 418.56-0ubuntu0~gpu18.04.1) but it is not going to be installed
                     Recommends: libnvidia-decode-418:i386 (= 418.56-0ubuntu0~gpu18.04.1)
                     Recommends: libnvidia-encode-418:i386 (= 418.56-0ubuntu0~gpu18.04.1)
                     Recommends: libnvidia-ifr1-418:i386 (= 418.56-0ubuntu0~gpu18.04.1)
                     Recommends: libnvidia-fbc1-418:i386 (= 418.56-0ubuntu0~gpu18.04.1)
                     Recommends: libnvidia-gl-418:i386 (= 418.56-0ubuntu0~gpu18.04.1)
E: Unable to correct problems, you have held broken packages.

Зависимости определенно существует, например:

$ sudo apt-cache showpkg xserver-xorg-video-nvidia-418
Package: xserver-xorg-video-nvidia-418
Versions: 
418.56-0ubuntu0~gpu18.04.1 (/var/lib/apt/lists/ppa.launchpad.net_graphics-drivers_ppa_ubuntu_dists_bionic_main_binary-amd64_Packages)
 Description Language: 
                 File: /var/lib/apt/lists/ppa.launchpad.net_graphics-drivers_ppa_ubuntu_dists_bionic_main_binary-amd64_Packages
                  MD5: a1eb1a42f08cae3b2102de9da0cd2b3b
 Description Language: en
                 File: /var/lib/apt/lists/ppa.launchpad.net_graphics-drivers_ppa_ubuntu_dists_bionic_main_i18n_Translation-en
                  MD5: a1eb1a42f08cae3b2102de9da0cd2b3b


Reverse Depends: 
  nvidia-driver-418,xserver-xorg-video-nvidia-418 418.56-0ubuntu0~gpu18.04.1
Dependencies: 
418.56-0ubuntu0~gpu18.04.1 - libnvidia-cfg1-418 (5 418.56-0ubuntu0~gpu18.04.1) xorg-video-abi-24 (16 (null)) xorg-video-abi-23 (16 (null)) xorg-video-abi-20 (16 (null)) xorg-video-abi-19 (16 (null)) xorg-video-abi-18 (16 (null)) xorg-video-abi-15 (16 (null)) xorg-video-abi-14 (16 (null)) xorg-video-abi-13 (16 (null)) xorg-video-abi-12 (16 (null)) xorg-video-abi-11 (16 (null)) xorg-video-abi-10 (16 (null)) xorg-video-abi-8 (16 (null)) xorg-video-abi-6.0 (0 (null)) xserver-xorg-core (18 2:1.19.6-1ubuntu2~) xserver-xorg-core-hwe-18.04 (0 (null)) libc6 (2 2.2.5) 
Provides: 
418.56-0ubuntu0~gpu18.04.1 - xorg-driver-video (= ) xorg-driver-binary (= ) nvidia-driver-binary (= ) 
Reverse Provides:

Почему не устанавливается автоматическая установка этих зависимостей?