I found a useful document about it: https://doc.orbeon.com/form-runner/component/attachment
Therefore I did a similar approach, I added this line in properties-local.xml:
<property as="xs:string" name="oxg.xforms.xbl.fr.attachment.allow-download" value="false"/>
but it doesn't work. When I created Form Builder and added attachment, the setting still marked allow download.
I think that you just have a typo. Try the following (with the property name starting with oxf
instead of org
). I've tried this locally and it is working for me.
<property
as="xs:string"
name="oxf.xforms.xbl.fr.attachment.allow-download"
value="false"/>