I fear you need to re-evaluate you approach a bit. Unity is an
engine, that basically means that you are just injecting some code of yours into existing structures. This is why concepts like the
Update()-Method exist.
LWJGL on the other hand is simply a java-binding for the raw OpenGL-API, the "graphic card's language" so to speak. LWJGL is a
library only, that means you basically have to write everything you know from Unity yourself, from asset handling to game logic.
A game loop is just one concept of how to build a game, albeit a broadly used one

.
In short, LWJGL is
NOT an engine. If you want to focus more on scripting and less on technical tasks that make a game tick, I would recomment you take a look at
this instead, which is much more
engine and less
library. Internally, it uses LWJGL.