At the linguistics conference, there were no / not / non- native speakers of Esperanto. They're all grammatically "valid", but they all mean different things - and pragmatically / idiomatically, only the no version is likely to be used.
hyphenation - Is the use of a hyphen between "non" and an adjective ...
"Non-" is defined as "a prefix meaning 'not,' freely used as an English formative, usually with a simple negative force as implying mere negation or absence of something (rather than the opposite or reverse of it, as often expressed by un-).