Controlling the brightness of LED panel via GPIO pins
That power supply included with that LED panel doesn't support dimming and any attempt to PWM its output may result in it malfunctioning. There are a large number of companies manufacturing and supplying constant current power supplies especially for LED panels. You just need to find one of the right current for your panel and with the correct output voltage range. (The light panel will have a nominal operating voltage despite being constant current operated.)

I have described PWM operation of a Mean Well power supply in my answer to 0-10V Digital Rheostat for LED Dimmer?. You may find this helpful.

The dimmer module you have linked to seems to be a phase control light dimmer. This also is not suitable to put in front of an SMPS. In addition, and as is common on Amazon and Banggood there is no datasheet so you can't be confident of specifications. "No datasheet? No sale!"