Can Jedi use legacy force lightning?

Solution 1:

Yes. The Legacy abilities are just that — usable by every character in your Legacy. There are no faction, class, or alignment restrictions on them; even a non-Force-sensitive class can use Legacy Force Lightning.

Your unlocked Legacy abilities are only usable after activating (and during) your Heroic Moment ability. They are unlocked by completing the Chapter 3 storylines for each class. You can view those unlocks by pressing Y to open the Legacy Panel and going to the "Imperial Classes" and "Republic Classes" parts of the "Global Unlocks" section at the top left.