The Marvell ESPRESSOBin (manufactured by GlobalScale) is a single board computer aimed at networking, storage, and connectivity. It features a Marvell ARMADA 3720 chip which can be used with Debian's arm64 port.

The Marvell ESPRESSOBin is available to order. Some of the early Kickstarter orders have been sent out already.

U-Boot

U-Boot support has been accepted for 2017.05.

UBOS Docs

The UBOS docs have a default uboot environment which I found useful as I forgot to dump mine!

https://ubos.net/docs/users/installation/espressobin.html

Armbian

There is a work in progress Armbian port.

https://www.armbian.com/espressobin/