The Samsung Galaxy A3 (2017) is one of Samsung’s more budget-oriented smartphones. Because of that, developer interest is not as abundant in comparison to other devices and there isn’t much by the way of official custom AOSP-based ROMs or custom kernels. That could be set to change though, as an official TWRP build has been released for the device and is available for download now! The download link can be found below.
You’ll need to flash it from within ODIN by following the steps found in this thread. Once you’ve done that, you’re good to go and can install any of the ROMs and kernels found on our forums! You can check out the official TWRP page here for the newly released build as well.