apt update && apt full-upgrade
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
find /etc/apt/sources.list.d -type f -exec sed -i 's/bookworm/trixie/g' {} \;
# Hold mdadm if it's in use
# apt-mark hold mdadm
apt update && apt full-upgrade
# unhold mdadm
# apt-mark unhold mdadm, then upgrade the rest
# apt update && apt full-upgrade

reboot

apt autoremove && apt clean
apt modernize-sources
#Caveat that trixie-backports might not have a Signed-By on some 3rd-party mirrors. You can fix this by manually setting Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg in /etc/apt/sources.list.d/debian-backports.sources

Deb13 uses tmpfs, so old files may still be in tmp directory. Check and remove

mkdir /mnt/tmp-chk
mount --bind / /mnt/tmp-chk
ls -lha /mnt/tmp-chk/tmp/
# remove files
umount /mnt/tmp-chk
rm -rf /mnt/tmp-chk

Kodi upgrade to 21.3 from multimedia repo:

apt-get install kodi:amd64=5:21.3-dmo0+deb13u1 libavutil58:amd64=10:6.1.4-dmo0+deb13u1 libvpl2:amd64=1:2.15.0-dmo1 libcdio19t64:amd64=1:2.2.0-dmo1+deb13u1 libcec7:amd64=2:7.1.1-dmo1 libcrossguid0:amd64=2:0.2.2+git200190529-dmo1 libiso9660-12:amd64=1:2.2.0-dmo1+deb13u1 libpostproc57:amd64=10:6.1.4-dmo0+deb13u1 libswresample4:amd64=10:6.1.4-dmo0+deb13u1 libswscale7:amd64=10:6.1.4-dmo0+deb13u1 libaribb24-0t64:amd64=1:1.0.3-dmo6+b1 libfdk-aac2:amd64=1:2.0.3-dmo1+b1 libopenh264-8:amd64=1:2.6.0-dmo1 libchromaprint1:amd64=1:1.5.1-dmo6+b1 librist4:amd64=1:0.2.11-dmo1 libavcodec60:amd64 libavcodec60:amd64 libkvazaar7:amd64=1:2.3.2-dmo0~bpo13+1

set quiet boot in /etc/grub.d/10_linux to 1