Plex changed the database engine from SQLite 3.7 to 3.8 (and later to a custom schema) around version 1.0.0. You cannot directly install Plex 1.40.x over 0.9.17.0.
Many early Western Digital and Synology units. plex media server version 0.9.17.0
To appreciate version 0.9.17.0, you must understand the climate of the time. This was before Plex introduced a dedicated movie rental store, before the heavy push for Plex Pass-exclusive hardware transcoding, and before the "discovery" features that now dominate the UI. In 2015–2016, Plex was still, at its heart, a tool for organizing your own media. Plex changed the database engine from SQLite 3