http://fab.wmflabs.org/maniphest/ has an "export to excel" button, I just noticed with horror. We're not going to advertise proprietary software in our issue tracker main page.
Possible solutions
https://github.com/PHPOffice/PHPExcel says ods is supported but then it's not in https://github.com/PHPOffice/PHPExcel#writing , so it appears to be only for reading; still, it supports export to CSV. Therefore, just call the button "Export to spreadsheet" (or "Export to CSV" if mentioning a specific technology is preferred).
This is IMHO an upstream enhancement request; but last time they told us we can also customise messages locally, I leave the decision to the admins (if and when we install that component; CSV export is useful so *something* needs to be available, can't tell specifics).
Upstream ticket: https://secure.phabricator.com/T5908