magento 2.4 show multiple table field in one ui grid column without a specific Column class

I have created a custom admin grid via xml component. The grid works, but I need to manipulate some of the data shown in the grid. I would normally create a class to assign to my column, something like this:

<column name="fullname" class="VendorModuleUiComponentListingColumnFullName">
...
</column>

Unfortunately, I can’t use it this time because the data manipulated via the $datasource, are not exported when clicking on the magento csv export button: the column title gets exported, but the column field is empty.

Is there a way to manipulate the grid content in a way that the result gets exported to the csv as well?