Flashing branded GL-AR150 to stock firmware

I have a GL-AR150 that was sent to me, and has a custom firmware on it. I absolutely never want to use the router for its original intention, so the custom firmware will never be useful for me. Instead of throwing it away, I want to flash the stock firmware on it instead. Is there a way to do so without knowing the existing firmware password or such nonsense?

Yeah, you just have to follow the debrick guide here:

And you want to flash the latest official firmware from here: