I have a Hewlett Packard zBook G5, with a generally successful Debian with Gnome install, initially 10.x (as current in January 2020) and recently upgraded to bullseye.
The installation is vanilla except that: a. It is installed on ZFS (including /) b. It has the nVidia proprietary driver and xorg (Nouveau was very sluggish) c. It is dual boot, with Windows on one NVMe device and Debian on another. Grub is installed on the Debian device and handles both Linux and Windows well. d. Several not-debian programs are installed on /opt and probably not relevant to any of the issues described below. There were several relatively low-impact but annoying issues, most of which evaporated with no effort beyond regular software maintenance. The one that remains is: Keyboard: the keyboard function keys to control screen brightness that (usually) do not work correctly but, instead, operate identically to the microphone on/off function key, including producing the same scan and key codes (as reported by showkey -s or showkey -k, on either a gnome or console terminal). Output from showkey -s 0x5a 0xda, and scancode -k reports keycode 190 press keycode 190 release. Irritatingly, on occasion they work correctly to control brightness. When this happens it may persist over several reboots. The brightness control in the Gnome settings power tab works as expected, and the buttons work normally when Windows is in control. 2. From time to time, while running, the screen freezes: keyboard input and mouse buttons do not work, although the pointer moves appropriately. Switching to a virtual console and back almost always corrects the problem. Suggestions on any of these defects will be gratefully received. The zBook is a very nice machine in most respects. I'm posting to both debian-laptop and debian-users since it is not whether this is exclusively a laptop type problem and apologize if that is inappropriate. Regards, Tom Dial