FWIW
I have a Hub and use a phone to control TV, DVD, DVR, etc and some X10. X10 control on the Harmony phone app is pretty lame. The hub sends X10 control via IR (not RF like the X10 remote) so you will also need a X10 IR543 "Command Center" to receive the IR codes from the hub and then put them on the house lines. X10 no longer makes the IR543 but you might find on Ebay or a Google search. The IR543 can only control one house code, so your X10 control is very limited. And expect NO help from Logitech Harmony. They are X10 clueless. AFA Alexa, I have not tried, but before trying to track down a IR543 I would email Harmony and confirm you can control X10 through the hub with Alexa. And if they say you can....keep the email.