https://gdpr-info.eu/art-20-gdpr/ reads
> 1. The data subject shall have the right to receive the personal data concerning him or her, which he or she has provided to a controller, in a structured, commonly used and machine-readable format and have the right to transmit those data to another controller [..]
https://gdpr-info.eu/art-4-gdpr/ reads
> ‘personal data’ means any information relating to an identified or identifiable natural person (‘data subject’); [..]
Exactly. Content in your website is not information relating to an identified or identifiable natural person. GDPR does not require a company to provide export of website content. It does have a requirement to export data they have stored about you though.
If however your customers are natural persons, you can migrate their data from a competitor (with their help and/or agreement).
Helping with the latter appears to be the point of Hotswap.