If by “meaningful” you mean “either true or false” and by “meaningless” you mean “neither true nor false”, then a Platonist and a formalist would disagree about the meaningfulness of the continuum hypothesis. Since I don’t know any knockdown argument for either Platonism or formalism, I defy everyone who claims to have a crisp answer to your question, including possibly you.
If by “meaningful” you mean “either true or false” and by “meaningless” you mean “neither true nor false”, then a Platonist and a formalist would disagree about the meaningfulness of the continuum hypothesis. Since I don’t know any knockdown argument for either Platonism or formalism, I defy everyone who claims to have a crisp answer to your question, including possibly you.