Animating Model with Rotation About Single Axis

I am currently using assimp to import various parts of a robot model but would like to animate/skin it in my OpenGL environment to simulate a range of motion.
To my understanding, this isn’t really supported in OpenGL especially since I am dealing with .obj files.
I was curious if there was an implementation to support joints that rotate about one axis/point in my model.

For reference a majority of my code follows this series:
assimp loading -
github repository -

I’ve also attached an image of a single joint in my model for visuals. Basically these parts interlock and should rotate within each other
Any help or direction would be appreciated!

Edit: My current attempt to implement this comes from however to my understanding the tutorial assumes you have a mesh that is already boned in some way whereas my .obj is missing this information which lead me to think I should implement my own vertex/bone struct in my code.