how do you install a hyphenation package?
This may not be necessary. Has your document ever been in contact with Google Docs? Google Docs is known to badly export to .odt.
This is tdf#137742
There does not seem to be hyphenation available for Greek. As @Ajlittoz hinted in the comment, you may not need it.
If you don’t require automated hyphenation
You can switch it off by editing the default paragraph style. See the Text flow tab.
If the hyphenation is not activated by style, you can disable it by manual formatting:
- Select all content (
ctrl-A) - Select menu item
Format-Paragraph - Select the
Text flowtab - Untick the first checkbox and click
OK
If you require automated hyphenation
The dictionary/thesaurus files may also contain hyphenation data. (I am guessing here, but worth a try).
You could try the downloads from this excerpt from the extensions or do your own search.
The extensions site is reached from the main LibreOffice site by selecting menu item Discover - Templates and extensions. There are also links in relevant dialogs in the LibreOffice apps.