I apologize. I misunderstood that you were looking for a mesh system that would work with an existing openwrt router. Seems what you're looking for is a mesh system that can be flashed with openwrt.
For that I can only suggest that you look at the supported hardware table and see if you can find what you need.
You have the option to get a solid hardware that you can install openwrt on, and then use the Deco mesh just for the Wifi. That'll give you similar, if not the same results, and save you a few bucks in the process.