In most countries, the output of a single prompt will not be copyrightable. However, once someone starts arranging the output into something more, then copyright can be applied.

Overall, it depends on the country, but in some they are asking their legislators for clarification. Many are trying to apply pre-existing copyright laws to LLMs.

The U.S. Copyright Office wrote up a report about this and included a list of how other countries are handling it.
https://www.copyright.gov/ai/Copyright-and-Artificial-Intelligence-Part-2-Copyrightability-Report.pdf