It is easy to blame the manufacturer, but the TB-X704F situation highlights a broader industry issue. Qualcomm provides driver support for chipsets for a finite period. The Snapdragon 625, while capable, is an older architecture. Furthermore, the profit margins on budget tablets like the Tab4 series are slim. Allocating engineering resources to port new Android versions, test them on older hardware, and push them OTA (Over-The-Air) is expensive.
: Navigate to the "System" or "About Tablet" menu. Check for Updates : Tap on System Update . Lenovo Tb-x704f Android Update