This answer is based on beeshyams's comment.
Download & install the SA Contacts Lite application; it is available on places where you don't need an account, e.g. via APKPure.com.
Start the app.
3.1 enable Export All Fields.
3.2 Disable Export Photos.
3.3 Enable Merge Duplicates.
Click Export, then Start.
A format selection dialog will come ...