I don't know how well Leon works but Mycroft is not running locally on your own server. It's still a cloud service. I believe it can be run locally but it's very complex and not well supported. At least this was the state last time I looked at it.

For this reason (and their failed Kickstarter) I've never really been into Mycroft. After all it's kinda the same as Alexa/Siri just a slightly more trustworthy party when they say they're not using your data.

I'm just not interested in alternatives until they can run fully locally (not necessarily on device, on a local server or docker is fine)

If this Leon does what it says on the tin it might be just the thing for me.