How to properly update amd64-microcode package in Debian Bookworm?

I have successfully upgraded my older UEFI amd64 Debian server to Bookworm. I am preparing for Trixie upgrade, but the following package just won't update:

# apt list '?narrow(?installed, ?not(?origin(Debian)))'

amd64-microcode/now 3.20250311.1~deb11u1 amd64 [installed,local]

...

while:

# apt-cache policy amd64-microcode

amd64-microcode:
  Installed: 3.20250311.1~deb11u1
  Candidate: 3.20250311.1~deb11u1
  Version table:
 *** 3.20250311.1~deb11u1 100
        100 /var/lib/dpkg/status
     3.20240820.1~deb12u1 500
        500 https://deb.debian.org/debian bookworm/non-free-firmware amd64 Packages
     3.20230719.1~deb12u1 500
        500 https://deb.debian.org/debian-security bookworm-security/non-free-firmware amd64 Packages

Could anyone help out, please? Thank you.

Reading sources I have been though already:

• Upgrades from Debian 12 (bookworm)

• Issues to be aware of for trixie

Update 1:

# cat /etc/apt/sources.list

# Debian 12 Bookworm https://www.debian.org/releases/bookworm/
deb https://deb.debian.org/debian/ bookworm main contrib non-free non-free-firmware
#deb-src https://deb.debian.org/debian/ bookworm main contrib non-free non-free-firmware


# Bookworm Security https://www.debian.org/releases/bookworm/
deb https://deb.debian.org/debian-security bookworm-security main contrib non-free non-free-firmware
#deb-src https://deb.debian.org/debian-security bookworm-security main contrib non-free non-free-firmware


# Bookworm Updates https://wiki.debian.org/DebianBookworm#FAQ
# https://wiki.debian.org/StableUpdates All packages from stable-updates will be included in point releases.
deb https://deb.debian.org/debian bookworm-updates main contrib non-free non-free-firmware
#deb-src https://deb.debian.org/debian bookworm-updates main contrib non-free non-free-firmware