LED lamps with halogen dimmer
50/60 Hz dimmers for nonlinear loads such as LEDs have stability issues at large phase angles where the voltage is dropping, so they use PFC to linearize the load. Recent chips  can handle power LEDs down to &lt; 1% power, flicker-free.

If you want a cheap and dirty solution, leave one filament bulb as a linear load in parallel with the rest being LEDs and that will work.

Mind you, the health risks from 120Hz flashing LEDs are being investigated for eye-brain strain, so PWM >1kHz is preferred.