On the openwrt forums (RIP) there was a thread about the Nexx WT3020 explaining step-by-step how to go from stock firmware to breed uboot before flashing openwrt/lede. There were also instructions on how to go back to stock, and links to the specific breed uboot rom image and stock image.
I still have the breed uboot rom and original stock image, but the thread with step-by-step instructions is no longer accessible. If memory serves me right, the specific post was made by some "alan" in the year 2011 I believe. Anyone has a copy of these instructions?