I still don't see the point of all this. If you have a handful of lights in a room, and drive them with a single power supply, you're still going to have big problems: the line lengths to each fixture will be different, resulting in different voltages. You can't drive LEDs that way with good results: they need fixed current. And you can't daisy-chain them either: if one emitter dies, then the remaining ones will suddenly have different current, and probably die quickly. The proper way to drive LEDs is with a power supply very close to the emitters and designed specifically for those emitters and the (short) wire length to them, not 4 meters away and not with some variable-length wire that can't be designed for.

Everyone here is complaining about ultra-cheap LEDs that don't last very long because they're poorly engineered, but that's exactly what you're all trying to do here by using a separate, shared power supply. You could get away with that in the 1980s using incandescent bulbs, but you can't do it now unless you want the same crappy lifespan and reliability you're all complaining about.

The solution is very simple: buy fixtures that are engineered well. Switch-mode power supply electronics are not expensive at all, but when mfgs cheap out or do a crappy job designing them, you get bad results, usually short lifetime of either the power supply or the LED. What you're trying to do here is buy a really expensive power supply, which has to be engineered to a far greater degree and for a far wider range of operating conditions (since they don't know what you're going to connect to it), just because you had a bad experience buying some $2 light bulb that had a crappy power supply built-in. This really makes no sense.