Skeletal Animation in C++

Frank Luna's book is a good starting point since it explains the math behind skeletal animation very well, and it also implements a demo without using external libraries, which always add complexity.

Then, you can take a look at other interesting resources such as

https://ogldev.org/www/tutorial38/tutorial38.html​

Game Engine Architecture (Jason Gregory)

Why write your own when you can use an off-the-shelf library? Try https://github.com/guillaumeblanc/ozz-animation.

Fairly good resource is:

https://learnopengl.com/Guest-Articles/2020/Skeletal-Animation​

The forementioned one from ogldev is also a great resource, although with slightly less explanation than the learnopengl one. Another (although a bit older) one was here:

https://www.3dgep.com/gpu-skinning-of-md5-models-in-opengl-and-cg/​

Personal note: Have a reference implementation somewhere near your hand that you can debug. Why? Simply because you may want to output and compare all transformation matrices in case you hit a problem. Also make sure you have simple skinned and animated mesh for testing.

I really like this video tutorial, but it's in Java. You can try translating the code to C++:

OpenGL Skeletal Animation Tutorial #1