The wait is finally over and Raspberry Pi OS is now based on the latest Debian GNU/Linux 12 “Bookworm” release and you can upgrade your Raspberry Pi right now. Here’s how!
The Raspberry Pi Foundation released new images for its Raspberry Pi OS that are based on Debian Bookworm. This is a major update that switches from X11 to Wayland by default with new apps, replacements for previous default apps, as well as other necessary adjustments.
The Bookworm-based Raspberry Pi OS also adopts PipeWire as the default multimedia backend and NetworkManager as the default network manager instead of PulseAudio and dhcpcd.
https://9to5linux.com/how-to-upgrade-raspberry-pi-os-to-debian-bookworm-from-bullseye