I have it set to not download updates automatically. LO started crashing yesterday. I finally saw that I had ver.5.2. Somehow it updated itself without my permission. I switched back to ver. 5.1. How do I prevent this?
Goto Tools|Options → LibreOffice → Online-Update and disable the corresponding option to auto-check for updates.
And LibreOffice doesn’t have a feature to automatically update itself. It only has a check whether new updates are available online.
So likely you added a repository to your linux distribution that carries the latest version and you did update by your distro’s package manger.