HOW TO REPRODUCE: 1. Insert any emoji into any kind of LibreOffice document. 2. Print or export as PDF. RESULT: - A blank is shown where the emoji should be.
Likely related: Apple Color Emoji not Visible in Exported PDF: https://bugs.documentfoundation.org/show_bug.cgi?id=94655
Alberto, perhaps you can confirm bug 128473. *** This bug has been marked as a duplicate of bug 128473 ***
*** This bug has been marked as a duplicate of bug 121327 ***