Here i am in March 2018, Samsung did not released Lollipop upgrade for Tab 4 SM-T230NU, and will never do. The latest official firmware from sammobile for this device is 4.4.2.
Alternative rom? Check this link for Acheron Rom 4.4.2 by @g_ding84. Works pretty well: https://forum.xda-developers.com/tab-4/development/rom-stock-t230-nu-acheron-rom-v1-0-2015-t3000107
archeron is outdated and slow. A best ROM is, https://androidfilehost.com/?w=files&flid=249452
I made that ROM.