if this is an initial install of LibreOffice on Ubuntu 20.04 please check:
- cups Authentication not working correctly
- Broken LibreOffice Installation on Ubuntu 20.04
- Lubuntu 20.04, LibreOffice 22.214.171.124. My Samsung ML 1610 printer does not print text correctly through LibreOffice. It prints graphics correctly
- on Ubuntu 20.04 LTS undefined symbol: png_set_option, version PNG16_0
- Cannot print anything, exporting to PDF produces blank PDF (Lubuntu 20.04)
All these problem - though looking completely unrelated - have in common being related to initial installations and share the same solution.
I think I messed up something with the system fonts, so did a system restore.