To Enable dark mode in latest #LibreOffice under #Ubuntu 20.04 LTS:
- Open LibreOffice.
- From menu, click Tools -> Options.
- Go to Application Colors, select document background as Black.
- If you would like to change to a dark icon theme, change it from View options on the left side for better visibility of the toolbar icons.
More Info > https://linuxapt.com/blog/17-enable-dark-mode-in-latest-libreoffice-under-ubuntu-20-04-lts