Cut the controller off and use the smart plug to control brightness. You might need to open it up and replace the power supply.

I'm going to guess that you will spend more money on this than just buying a light that has smart features compatible with your smart home ecosystem. You can't mix two smart systems on one cord - this has never worked. Where to put the smart is a tricky question as there are pros and cons to every answer, but in general the smarts need to be in exactly one place or things won't work.