That's very good news: if you already have a working Uboot & Kernel from the vendor, installing OpenWRT is possible. The architecture is armv7a so you can, as I told you:
use U-boot from your vendor
use the kernel & moduleset from your vendor
get OpenWRT from Raspberry Armv7a (i would go for something like Raspberry Pi 2B/2B 1.2 (32bit)
modify it to make it boot on your board, providing it boots with your kernel, proper Uboot parameters etc.
It's non-trivial but definitely possible.
You should start booting with the distro your vendor provides (whatever it is) and work from there.
BTW: I red from the product brief that this board has only 10/100 cards, which makes sense, but it's a very weak board overall for modern, gigabit or 500mpbs+ setups.