I am guessing you are talking about practical endgames and not chess studies.
Two great resources are the texts:
100 Endgames You Must Know: Vital Lessons for Every Chess Player and
100 Endgame Patterns You Must Know: Recognize Key Moves & Motifs and Avoid Typical Errors by Jesus de la Villa.
The author breaks down in the first book in what I find to be digestible parts.
The second book provides examples that are still theoretical, but stretches concepts from first book.
A player could enter them on her/his computer and play against an engine for practice.
If those texts are over one's head, I will recommend Silman's Complete Endgame Course: From Beginner to Master by IM Jeremy Silman, which I find a thorough starting place for many students of the game.
I am around 2100 lichess and I feel like it would be a good idea to dedicate more of my time to studying endgames. The problem is that there are so many different possible moves in each position that I basically can't calculate anything, and I don't know how to learn the basic principles of each type of endgame.