Is there a viewer for Writer?

edit

There's not a standalone viewer application, but you could select all the content and protect it (prevent it from being edited) with a password, as described here: https://help.libreoffice.org/Writer/P...

The .pdf format (Portable Document Format) is designed to provide the formatted document just to be viewed. In LibO you can select this format as File > Export as > Export as PDF. This allows someone to view but not change a document. Document formats such as .odt / .doc /.docx etc. are revisable and not intended for read only display, and can look different on different systems depending on the individual setups.

Most users already have a .pdf viewer installed. This is smaller and faster than using a full office system to view the original source document. In addition, you keep the original source and can protect it from anyone having access to it. Although it is possible to modify the .pdf on some systems, this only gives access to a formatted copy, not the original .odt file, with its inherent usage statistics.

If somebody can access your document, they can probably move it to a medium where they can open it for editing.

If an organization needs to make sure someone views some documents without possibility to edit them on a SharePoint instance, that should be done using SharePoint policies (assigning proper access rights, etc), not by installing read-only apps.