Try to be as open as possible to the community, making it possible to enroll in beta testing early, enable people to contribute even before a device is released to the masses.
One possibility would be to enable people in the community to buy pre-series devices for a significant discount (don't have to be completely free for all of them, maybe on a price that is those community beta testers/developers just replacing production costs and not actually "buying" them). Could also involve people singing some NDA and/or agreement to help market the device in forms of blogs/forums/social media to get access to more pre-releases info etc.

Also, include the existing Maemo/MeeGo/Mer/... community, don't try to cook your completely separate thing in terms of community, but build bridges to existing communities.

If you want community involvement, you can even get community helping to make the product you ship better, but you need to actively engage them and make them feel as a part of the movement, being treated in a fair and open way.
Even Nokia didn't fully manage to get that done - Jolla might have a chance to do that.