Update: the text below refers to Debian 10 "buster". Now that Debian 11 "Bullseye" has been released, which has Linux kernel 5.10, things should work out of the box. I just did a dist-upgrade from buster to bullseye which was the smoothest dist-upgrade that I ever had, i.e. no problems at all. Except that I had to do a apt-get install linux-image-amd64 to get the standard bullseye kernel (my kernel installed manually from buster did confuse VirtualBox which complained about mimssing matching kernel header source files) .

The Thinkpad T14 AMD is a very nice machine and everything works with Linux (I did not test the fingerprint reader and infrared camera, though). I opted for the T14 over the slimmer T14s, because the T14s has no full sized Ethernet port and it seems that (due to being slimmer) the cooling is not as good as with the T14.

Kernel 5.9 (or later) is a must to support all the hardware of Thinkpad T14 AMD, but the 4.x kernel used by the installer of Debian Buster is sufficient to do the installation, except that Wifi does not work, so you need an Ethernet cable connection during installation.

To get the 5.9 kernel in Debian Buster, it is at time of writing available from Sid (there are various ways to use packages from Sid in Stable -- in the simplest case, download the debs manually), and the following packages are needed:

• linux-image-5.9*-amd64*
• firmware-linux-free*
• firmware-linux-nonfree*
• firmware-misc-nonfree*
• firmware-amd-graphics*
• amd64-microcode* (Checking that the UEFI/BIOS is most recent before using a Microcode upgrade is recommended. But the update might be anyway blocked via /etc/modprobe.d/amd64-microcode-blacklist.conf)

In principle, the kernel header files are also nice to have, but it may involve updating to a completely new GCC from Sid:

• linux-headers-5.9*-amd64*
• linux-headers-5.9*-common*

Note that you will not get automatically security updates if you update the kernel manually. You may want to give APT pinning a try for having only the kernel from Sid.

Update: a buster backport of a more recent kernel is available now, install via apt-get install -t buster-backports linux-image-amd64 (assuming, you have backports configured). This support also all the above packages, including linux headers.

Note that for the Intel AX200 Wifi to work, you also need the latest firmware-iwlwifi (the one from buster-backports is enough-- the one from Sid should not be necessary):
apt-get install --target-release=buster-backports firmware-iwlwifi (assuming that backports have been configured as APT source). Initially, I had to download some files directly from Intel, but it seems that the buster-backport package now contains the missing files.

The graphics was straigthforward from Debian Stable:

• xserver-xorg-video-amdgpu
• firmware-amd-graphics*

I cannot remember whether I installed them explicitly or whether they are just installed because they are dependencies of the above AMDGPU package: I have a couple of mesa and DRM packages installed (see also Debian Howto on AMDGPU and the Debian Page on Video acceleration), e.g.:

• libgl1-mesa-dri
• libglx-mesa0
• mesa-vulkan-drivers
• mesa-va-drivers (for video decoding)
• vdpau-driver-all (for video decoding)
• libdrm-amdgpu

(The whole Linux graphics stack consists of more components, you maybe want to check..)

Check whether MESA is activated.

Also some, BIOS/UEFI tweeking was needed, e.g. Change sleep state from Windows to Linux mode (and if you use an unsigned kernel: disable secure boot).

There is one thing concerning suspend and resume, though: my Jabra USB headset stops to work after resume -- manually unplugging and plugging the USB plug solves this problem and remarkably other USB devices (keyboard and mouse) work after resume. In the end, I wrote a script that removed and install the USB module after resume and placed as file /etc/pm/sleep.d/10-usbquirk.sh (do a chmod a+x). The content is as follows:

# !/bin/bash
# USB headset not working after suspend, so try relode USB module (other USB devices work though)
case "${1}" in
hibernate)
;;

suspend)
;;

thaw)
rmmod xhci_hcd
sleep 0.5
modprobe xhci_hcd
;;

resume)
rmmod xhci_hcd
sleep 0.5
modprobe xhci_hcd
;;

*)
;;
esac

(Somehow the indentation got removed by WordPress -- but in fact indentation does not matter for the Bash script.)

I also have the UltraDock docking station: it uses the two USB-C ports of the T14 plus a third proprietary connector: AFAIK it is for the Ethernet, even though it seems that it does not simply mechanically extend the Ethernet port, but has an extra Ethernet chip built-into the docking station. And I guess that one of the USB C ports works rather in a mode where not USB C is used but the video signals are directly transmitted, so that is different from a pure USB C dock. And indeed, the dock seems to have its own MAC address (I did not figure out how to find out what the MAC address is -- probably need to connect it to my smart switch). While the BIOS has a MAC passthrough setting (that is enabled), under Linux, it gets not passed through.

Otherwise, the dock works without any extra configuration with Debian, including dock and undock (I use a 4k screen via one of the HDMI connectors of the UltraDock and a couple of USB A ports of the UltraDock).

I still dislike not having anymore the bottom dock connector used by Lenovo in the past: you cannot anymore simply "throw" the Laptop onto the dock, but need significant force now to insert the three connectors from the side and I am not sure, how many docking cycles the USB-C connectors last from a mechanical point of view.

I also tried a 4K screen (Lenovo P32p) that has USB-C for power delivery and video and even serves as USB hub as well (i.e. with one USB-C cable, it powers the laptop, transmits the video, and mouse and keyboard are attached to the screen; it even has Ethernet that will then go via the same, single USB-C cable). This works nice and replaces in fact a dock. -- However, at the beginning I needed always to reboot the system in order to make the video work via USB-C. For some reasons this problem magically disappeared.

TODO: Check Thinkpad specific packages (I have them currently not installed, and do not see any hardware support missing).

Update: There is now also Debian Wiki page on the Thinkpad T14.