Yes, PERIFACT now also supports UBL 2.1 invoices.
A UBL invoice is a standard XML format used by the government to create electronic invoice send. It is a format that allows digital invoices to be read into an accounting program in a relatively simple manner using standardization.
Would you also like to attach a UBL file by default when sending your PDF? Go to the menu SETTINGS - EXTRA's and choose the tab [Email]. There you can enable that both the PDF and the UBL file are sent along.