Use Alexa to issue on/off commands to dimmers
"Alexa, turn living room light on" only works if the light is a switch rather than a dimmer. If it's a dimmer, then you have to specify the level.
You should have the ability to just use on/off for dimmers in the same way as switches, as having to use a level is a bit awkward. "On" should set the dimmer to the last level used.