I want to completely uninstall this program. How do I do it? I’m sure there is more to it than just deleting the program from Applications.
If you start up LibreOffice and go to Preferences → Paths (translated from Finnish so might be slightly different) you can see the paths that LibreOffice is using. You can go ahead and delete the files in those paths if you do not need your LibreOffice preferences anymore. Then you can delete the application from /Applications or wherever you installed it to.
You could use a third-party application like AppCleaner to safely remove all components of LibreOffice.