GNU/Linux Debian Bookworm Installing AMD Open Source Drivers Guide
How to Install AMD Open Source Graphics Drivers on Debian Bookworm 12.x GNU/Linux – Step by step Tutorial.
And Open Source AMDGPU Graphics Drivers for Debian 12 includes Updated Free Graphics Drivers for AMD/ATI Graphics Cards.
These drivers are based on the Mesa 3D stack and support modern AMD GPUs using the AMDGPU kernel module.
Especially relevant: as for Debian policies all the Non-free Firmwares are non included in the Default Repository.

1. Launching Shell Emulator
Open a Terminal window
(Press “Enter” to Execute Commands).
2. Enabling Non-free Repo
How to Add Debian Non Free Repo Preserving System
3. Installing AMD Open Source Drivers
Then to Install AMDGPU Open Source Graphics Driver on Debian
First, you are strongly Recommended to Upgrade your System with:sudo apt upgrade
In this case then Reboot:sudo reboot
And to Setup the Amdgpu Driver run:sudo apt install xserver-xorg-video-amdgpu firmware-amd-graphics ricks-amdgpu-utils
The Command includes also the Utilities for adjustment and monitoring.
And for the Legacy ATI Cards possibly:sudo apt install xserver-xorg-video-ati firmware-amd-graphics ricks-amdgpu-utils
Last, to load it Reboot:sudo reboot
So Now I’m truly Happy if My Guide could Help you to Install AMD Open Source Drivers on Debian Bookworm!