How can one open an XML file with LibreOffice?

If the file is an XML table, you can open it in LibreOffice Calc through the Data > XML Source menu¹. Inside it, you just need to open the XML file, point to the table you're importing on the left column and specify a destination in your sheet in the right text field. Example:

This feature is documented in the Help for LibreOffice Calc and at https://wiki.documentfoundation.org/Development/Calc/XMLSource .

¹_{Since this is an experimental feature (at least in V 6.1.3.2), it may be unreliable and the menu entry will be greyed out unless experimental features are enabled with Tools – Options – LibreOffice – Advanced – Enable experimental features.}

You can also use basex from the software center.

sudo apt-get install basex

BaseX is a very fast and light-weight, yet powerful XML database and XPath/XQuery processor, including support for the latest W3C Full Text and Update Recommendations. It supports large XML instances and offers a highly interactive front-end (basexgui).

I don't have it installed but it has really high ratings from the software center.