For me it looks like the above is the problem. One package wants to overwrite file '/etc/kernel/postinst.d/z50-raspi-firmware', but this file is also needed by package armbian-bsp-cli-rpi4b-current 25.2.3. So it can’t be overwrtten.
It seems to be an know issue read: Keine Updates oder Installationen mehr möglich wegen fehlender Firmware oder Bootloader (german) and the in that german forum linked solution from Rob Latour: sudo apt upgrade / sudo apt full-upgrade fails - raspberrypi-bootloader but it is not installable or raspi-firmware but it is not installed (english).
Oh and the last Link directed me to Internal Server Error After Php8.3 Upgrade on 12 Apr NCP 1.55.3 on RPi5
So the problem seems to be caused by Update to PHP8.3 on RPi’s.