This is no joking matter.; This is no joke.

这可不是闹着玩儿的事。

《新英汉大辞典》

This is no joke. Real people.

这不是玩笑，是真人真事，真的奋斗经历。

youdao

This is no joke, I assure you.

我发誓，这不是开玩笑。

youdao

Except this is no joke.

FORBES: While Congress fiddles, lawyers finagle.

No, no one who tells the joke nor I in repeating it think that this is the best path: or even an acceptable one.

FORBES: The Appalling Greek Solution: A Military Coup

Perhaps not, but there is no doubt that this show relentlessly entertains from start to finish as it hurtles you past joke after joke with little recovery time.

BBC: The Right Size fit the bill