LED lights are great for saving energy compared to their older incandescent counterparts. However, being able to dim LED lights has proven to be challenging. Where incandescent lights had nothing more than a filament inside (piece of wire that glowed), LED lights have electronics inside. The first generations of LED lights couldn't be dimmed at all. Newer LED bulbs can be dimmed but this is meant for use with a standard old school dimmer and not necessarily the electronic dimmers we find in smart switches. There is little consistency from one production run to the next, from one model to another, or from one brand to the next. In order to drive prices down on LED bulbs, cheaper components are sourced, designs are changed, etc.
So that said, just because the bulb says it's dimmable doesn't mean it's going to dim nicely when used with an electronic dimmer. While this article is discussing primarily Insteon dimmers, it is relevant with respect to many other products including UPB, ZWave and so on. Even when the bulb is dimmable and the dimmer says it works with LED bulbs, you may find that the bulbs don't dim smoothly, may flicker, or may flicker when they get down to a certain level of brightness.
For that reason it's important to do your due diligence and test the bulbs you wish to use, with the dimmers you wish to use. If the bulbs don't work nicely, you'll need to try another bulb.
Insteon dimmers are "forward phase" dimmers so when dealing with lighting manufacturers, make sure they are compatible with forward phase triac dimming. Get a sample before you fit the whole house with custom lighting.
In the case of simple screw-in LED bulbs, the cheapest ones may work - or they may not. Don't blame the dimmer for a cheaply made bulb!
We've found that the Philips warm glow bulbs seem to "play nice" with most smart dimmers including Insteon. Plus their colour temperature is very similar to incandescent lights and they also use 2 sets of LEDS. The second set turns on at lower levels to provide a much better low level dimming experience.
If you're stuck in a position where you can't change the LED light to solve flickering problems, you can try checking to see if there is any AC noise causing the electronics to be unstable. It may not be the dimmer or bulb's fault but rather some noisy, cheaply made power supply of some sort. Try turning off other circuit breakers around the home to see if flickering stops or is reduced when another load is turned off.
There is also a product available called an LED stabilizer
that can be installed in the dimmer or light junction box that may reduce or eliminate flickering.
Steve Lee from Insteon created a great video discussing LED dimming and how to troubleshoot. If you're having issues please take a few minutes to check it out: https://youtu.be/249cU5tvIAs