Apt가 데비안 백포트 펌웨어를 찾을 수 없습니다

Debian Bookworm 백포트를 사용하여 amdgpu 펌웨어를 업데이트하려고 합니다. /etc/apt/sources.list.d/backports지침에 따라 이것을 추가하고 무료가 아닌 항목을 추가했습니다 .https://unix.stackexchange.com/a/467108/50441무료가 아닌 펌웨어

~$cat /etc/apt/sources.list.d/backports.list
deb http://deb.debian.org/debian/ bookworm-backports main contrib non-free-firmware non-free

커널을 잘 업데이트할 수 있습니다.

~$apt policy linux-image-amd64
linux-image-amd64:
  Installed: 6.6.13-1~bpo12+1
  Candidate: 6.6.13-1~bpo12+1
  Version table:
 *** 6.6.13-1~bpo12+1 100
        100 http://deb.debian.org/debian bookworm-backports/main amd64 Packages
        100 /var/lib/dpkg/status
     6.1.85-1 500
        500 http://security.debian.org/debian-security bookworm-security/main amd64 Packages
     6.1.76-1 500
        500 http://deb.debian.org/debian bookworm/main amd64 Packages
     6.1.67-1 500
        500 http://deb.debian.org/debian bookworm-updates/main amd64 Packages

그러나 백포트된 펌웨어 버전은 apt에 표시되지 않습니다.

~$sudo apt-get install firmware-amd-graphics/bookworm-backports
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package firmware-amd-graphics is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Release 'bookworm-backports' for 'firmware-amd-graphics' was not found

에서 찾을 수 있었어요https://packages.debian.org/bullseye-backports/firmware-amd-graphics수동으로 다운로드했는데 이상합니다.

~$apt policy  firmware-amd-graphics
firmware-amd-graphics:
  Installed: 20230210-5~bpo11+1
  Candidate: 20230210-5
  Version table:
     20230210-5 500
        500 http://deb.debian.org/debian bookworm/non-free-firmware amd64 Packages
        500 http://deb.debian.org/debian bookworm/non-free-firmware i386 Packages
 *** 20230210-5~bpo11+1 100
        100 /var/lib/dpkg/status