Moving CMS content between sandbox and production
Key Takeaway
CMS content is data, not metadata, so you can't deploy it. You move it by exporting it from a CMS workspace in the sandbox and importing it into a CMS workspace in production.
Content you build in Salesforce CMS, such as images, news, documents, and custom content types, doesn't move from a sandbox to production the way configuration does. You export it as .zip archives from a CMS workspace and import those archives into a CMS workspace in the destination org. To do it well, you import media before the content that uses it, decide whether to publish on import, and recreate CMS Collections by hand.
Why you export instead of deploy
Only metadata, meaning settings, can be deployed. CMS content is data, not metadata, so you can't deploy it from one sandbox to another or from a sandbox to production. Instead, you export the content from a CMS workspace in the source org and import it into a CMS workspace in the destination org.
A sandbox refresh updates metadata from the source org. Only Full sandboxes support CMS content and collections. Partial Copy sandboxes don't copy CMS content.
Ana's team builds news items and images for a new product line in a Full sandbox. When they deploy their settings to production, the news items and images stay behind, because CMS content is data. Ana exports the content from the CMS workspace in the sandbox. Then she imports the .zip archives into a CMS workspace in production.