I've got Alexa controlling my X10 setup nicely.
The lights come On/Off before she says OK most times.
Setup was fairly easy once I figured out the scripts to create, which Alex10 now creates for you.
HA-Bridge which Alex10 uses will control many other brands of devices and lights even some that aren't considered a HA device.
Of coarse there is no documentation for that.
My wife keeps asking when Alexa will turn on my non smart TV. However when I ask if she wants that, she says she wouldn't use it!
The cool thing about Alexa is no voice training was done even though that is still possible.
Very rarely does she not understand a command.