Khadas Vim is a development board powered by Amlogic S905X quad core processor that officially supports Ubuntu 16.04, OpenELEC and Android 6.0. Shenzhen Wesion Technology , the maker of the board, has now released Android 7.1 firmware image and SDK for the board.
If you want to give it a try on your board, download Vim_Nougat_170321.7z directly, or from the firmware download page. The current image installs to the eMMC flash via USB or a bootable micro SD card (Windows methods only), so it will wipe whatever OS you have already on the board.
The firmware is based on the features of their Android 6.0.1 image, but upgraded to Android 7.1.1 with Chrome and Gapps (for Google Play Store support).
Source code for the Android 7.1 SDK can be found via several repositories on Khadas Github account. Once the manifest file is updated, you should be able to follow the instructions to build Android for Khadas Vim board in order to build your own Android 7.1 image from source.