I second this. When my home was infested by flies (I stopped counting at ~1000 over a 3 week period) they would always swarm and hang out by my grow lights (full spectrum LEDs) in my kitchen window. It was a great place for fly traps on the flip side.
It is quite possible that flies prefer one part of the light spectrum more than another part, but to say in the title that they don’t swarm at LEDs is misleading at best.
Might be something to do with PWM.
Also the light bulbs have excellent performance at "catching" bugs because they land on hot stuff and die. I had some GU-12 ceiling halogen lights in my previous apartment and the rims were always covered by bugs that decided to land there and as they were hot from halogens, boom, bug destruction machine