The directory for the default language is something that you can turn off from WPML settings.
Please kindly follow the steps below:
- Go to "WordPress Dashboard > WPML > Languages > Language URL Format".
- Make sure that the "Use directory for default language" checkbox is Unchecked.
- Click the "Save" button.
- Go to "WordPress Dashboard > Settings > Permalinks".
- Click the "Save" button to flush the permalinks cache.
- Follow the steps to re-run the XML Sitemap feature of Rank Math.
If you still have issues with the sitemap please kindly contact Rank Math support as mentioned in the doc below: