you can download the image file in this website:
and the openwrt source files:
I added the APK package manager in this image, you can use it to download the APP. For example, python3, pip, gcc.
But if you use APK, you must run the " network-init.sh" bash script to init your network and download some packages to make sure you can use the APK package manager properly.
It already adapted to the duo, duo256m and duos. However, the arm core`s openwrt still cannot be used.