This version comes with some bug fixes including
* Recalculation of matrix formula dimension correctly.
* Toggling grammar checkbox deletes sentence
* Random crash while dropping texture
* Handing in slideshow. (fdo#32861) [Thorsten Behrens]
* Crash on closing document with footnotes.
You can read the changelog here.
If you want to install version 3.4.4 on your Ubuntu PC and want to keep it updated you can add this PPA to the repository and then searh and install the latest version of LibreOffice on your PC.
You can also download LibreOffice from here.