After several months of trying (without really trying), I finally managed to remove my faulty ceiling LED fixture. I was expecting a standard LED bulb once the beast dismantled, alas not.
I am unable to identify the piece. The LED is encased in some sort of a radiator, and the connection looks like a circular plug used in some laptop charger (with little stoppers to fix it in place). I don't think the ceiling fixation should be included in the product, I just forgot to remove it before taking the photos.
Additional info: I live in France. The cable is chinese (I read "52(RVV)" on it), and I can barely read on the white plastic around the semiconductor; something like DEC2508-135135 or DEO2508-135135. Outer size (diameter) of the plug is 5mm. I can take more photos if needed.
Edit: I don't think I can replace a smaller part than the whole piece. See third photo.
Edit 2: following Harper answer, which I agree with, I forgot to say that I don't think the LED per se is at fault, because the light sometimes lights up when moving the whole when plugged-in. But, my question still stands; if I cannot repair it, how can I identify the whole device and where can I buy a replacement?
Follow up: I pulled the cable from the ceiling, I found a LED power supply (Model KEDH008S0200NR05, converting from 230 V to about 24 V) that emit a very faint alarm when the switch is on. It might be the source of the problem. I am no professional, and my landlord has no idea where to buy this.