I just saw the announcement of Home Assistant's "Voice Preview", an open source alexa/google home/siri, and have ordered one on a whim.
For years I was following Mycroft which I was hopeful for but they had so many issues I never had confidence to put my money into it. Then they finally had a preorder of their product and it was like $200USD, and then eventually they folded. I have much more faith in Home Assistant delivering considering all their work on voice so far, and also it's a real product already ready to order and costs $59USD. So I ordered one on a whim.
It's called "Preview" because they don't think the experience is ready for the average home yet, better for early adopters and tinkerers. I am more than happy to tinker so I have taken the dive and am keen to see how good it is.