Debian kernel with Apple T2 patches built-in. Kernels are build on debian unstable.
The kernels are based on T2 Ubuntu kernels. The build periodically (6h) checks for changes and in case of a change, grabs build parameters, patches and driver repositories to build a new set of debian packages.
Download the .deb packages of linux-headers and linux-image of the kernel you wish to install from the releases section.
Enter the directory where the packages has been downloaded to, and run:
sudo dpkg -i linux-headers*.deb && sudo dpkg -i linux-image*.deb
Restart your Mac.
Consider removing previous images:
dpkg -l linux-image\*
apt purge linux-{image,headers}-<insert-version-here>*
Please visit T2 Ubuntu kernels.
Special Thanks to @AdityaGarg8 for maintaining the T2 Apple Ubuntu kernel images