The adverb 无非 is used to soften the meaning of what has been said. Moreover, it is used to emphasize that a situation is not that serious.
无非 is often followed by a noun used as a predicate. The copula verb 是 connects 无非 and the predicate.
It is just a matter of time
wúfēi shì ge shíjiān wèntí
All he needs is a stable job
tā xiǎngyào de wúfēi shì yí fèn wěndìng de gōngzuò