Armbian is a lightweight Debian or Ubuntu based distribution specialized for ARM developing boards. It is compiled from scratch, has powerfull build and software development tools, and a vibrant community.
Armbian supports a wide variety of Allwinner A10, A20, A31, H3, A64 boards.
Legacy kernel is no more supported
As of October 6, 2019 Armbian dropped support of kernels older than 4.0, which obviously effects frequently used sunxi-3.4 and sunxi-3.10 kernels. It may be more convenient for some to use these kernels for the sole purpose of utilizing VE and GPU with a batteries included distribution like Armbian, until Cedrus and Mali Open Source Driver completely make it to the matured, ready to download distribution images.
You can apply the following dirty hacks to compile an Armbian image with Ubuntu Xenial Xerus rootfs image containing legacy kernel.
Clone v19.08 branch, the latest one with the legacy kernel components
git clone -b v19.08 https://github.com/armbian/build.git
Add legacy kernel option
Check if the board configuration file which you are planning to use has default option listed in its KERNEL_TARGET variable. Board configuration files can be found under build/config/boards directory.
Change compiler version
Unfortunately it is not possible to use legacy 3.4 kernel with GCC version above 4.9 without patching the kernel. Make sure that your target board family source file, listed under build/config/sources has KERNEL_USE_GCC='> 4.0' value for default branch.
Now you can execute ./compile.sh and start compiling an Armbian image.