I created a program to download data from Omeka Classic. It is published in the following repository.

I also created a Google Colab notebook that demonstrates how to run this program.

In the above tutorial, data download is performed targeting the following Omeka Classic site.

After execution, the API download results are output to the docs folder.

You can use the above data for backups, etc. I hope this serves as a useful reference when using Omeka Classic.