LibreOffice version 7 is using the hardware-accelerated text rendering engine called Skia which is unsupported in SuperNova
While we investigate the possibility of supporting the changes in LibreOffice 7, we recommend that any users that need access to LibreOffice use the version 6. Version 6 of LibreOffice can be downloaded from:
Once LibreOffice 6 is installed ensure that the accessibility mode is enabled (in Tools > Options). And also, in the “View” group of options, uncheck “Use hardware acceleration”, “Use anti-aliasing” and “Use OpenGL for all rendering”.
After applying these changes quit and re-start LibreOffice 6.