HOWTO: Upgrade Raspberry Pi OS from Bookworm to Trixie

gistfile1.txt

### WARNING: READ CAREFULLY BEFORE ATTEMPTING ###
#
# Officially, this is not recommended. YMMV
# https://www.raspberrypi.com/news/bookworm-the-new-version-of-raspberry-pi-os/
#
# This mostly works if you are on 64bit. You are on your own if you are on 32bit or mixed 64/32bit
#
# Credit to anfractuosity and fgimenezm for figuring out additional details for kernels
#

# Make sure everything is up-to-date
sudo apt-get -y update && sudo DEBIAN_FRONTEND=noninteractive apt-get -y dist-upgrade

# Point to bookworm repos instead
sudo sed -i -e 's/bookworm/trixie/g' /etc/apt/sources.list
sudo sed -i -e 's/bookworm/trixie/g' /etc/apt/sources.list.d/raspi.list

# Contents of /etc/apt/sources.list
deb http://deb.debian.org/debian trixie main contrib non-free non-free-firmware
deb http://security.debian.org/debian-security trixie-security main contrib non-free non-free-firmware
deb http://deb.debian.org/debian trixie-updates main contrib non-free non-free-firmware
# Uncomment deb-src lines below then 'apt-get update' to enable 'apt-get source'
#deb-src http://deb.debian.org/debian trixie main contrib non-free
#deb-src http://security.debian.org/debian-security trixie-security main contrib non-free
#deb-src http://deb.debian.org/debian trixie-updates main contrib non-free

# Contents of /etc/apt/sources.list.d/raspi.list
deb http://archive.raspberrypi.org/debian/ trixie main
# Uncomment line below then 'apt-get update' to enable 'apt-get source'
#deb-src http://archive.raspberrypi.org/debian/ trixie main

# Do actual update. See also https://forums.raspberrypi.com/viewtopic.php?t=389477
sudo apt update
sudo apt full-upgrade -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confnew" --purge --auto-remove rpd-wayland-all+ rpd-x-all+
sudo apt -y clean && sudo apt -y autoremove

# Reboot
sudo reboot

# Modernize sources
sudo apt modernize-sources

# Make sure the following is in /etc/apt/sources.list.d/raspi.sources. The Signed-by: may be missing
Types: deb
URIs: http://archive.raspberrypi.org/debian/
Suites: trixie
Components: main
Signed-By: /usr/share/keyrings/raspberrypi-archive-keyring.gpg

# Remove the raspi.list.bak after confirming that everything works
rm /etc/apt/sources.list.d/raspi.list.bak

had the "signature year" prolbme
apt install --reinstall raspberrypi-archive-keyring

solved it.
FYI for future me if I have the same problem.

Did you upgrade the kernel? That would be a starting point. What does „no boot“ mean, any details? Otherwise, roll back by restoring your backup.

I still have 6.12.34+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.34-1+rpt1 (2025-06-26) this kernel how did you update?