Like some other Linux distributions, the Raspberry Pi OS is built on top of Debian. Debian, on the other hand, recently received an update from Debian Buster, on which the Raspberry Pi OS was previously based, to Debian Bullseye. Raspberry Pi has now announced that the Raspberry Pi OS will also be based on this new Debian version in the future. But while the Bullseye release itself mainly involves changes that are barely visible to the user, adjustments have been made to the desktop environment and thus also to the hardware requirements for the Bullseye-based Raspberry Pi OS.
 
Source: Raspberry Pi

GTK + Version 3 Is Coming

GTK + is a toolkit that allows you to create widgets and GUIs. So far, the Raspberry Pi OS has used version 2 of the toolkit. Since GTK 2 has reached the end of its life, the migration to version 3 of the toolkit had to be carried out. All applications and tools within the Raspberry Pi OS that use the GTK had to be tested accordingly and patched if necessary.

Mutter, a New Window Manager

If you want to have windows managed on Linux, and thus on the underlying X server, you need a window manager. So far, this has been implemented by openbox, a small, slim window manager. However, in the course of the switch to GTK + 3, it was necessary to switch to the window manager mutter. This window manager does not write application windows directly to screen memory; rather, each window has its own memory area in which it is drawn. Then the whole thing is put together by mutter to a desktop picture and transferred to the GPU. This makes nice-looking desktop effects possible. However, this drawing process for the desktop uses significantly more RAM than before, so the mutter can only be used on a Raspberry Pi 4 with 2 GB of RAM.

KMS video driver

The KMS (kernel modesettings) display driver was previously experimental and is activated by default from this release. The previous display driver was Raspberry Pi-specific and represented a closed-source component. With the KMS display driver, the Raspberry Pi now has a way to address the display via the Linux APIs without the need for special adaptations. With the driver as part of the Linux kernel, it can now also be expanded by third parties.

A New Camera Driver

The control of the camera modules by the Raspberry Pi is now carried out by libcamera, a standard Linux API. This means that less proprietary code is used here too, so that the development of new camera software and hardware by third-party providers should become easier.

Raspberry Pi OS: A New Image

A new image with the current Raspberry Pi OS is available. If you want to use it, you should write it to an SD card as usual. An upgrade for an older Raspberry Pi OS to the current version is being worked on.