Anatomy for digital artists is taught badly in most online resources because it conflates anatomy knowledge (what is this structure) with anatomy application (how do I draw this convincingly from imagination). These are different skills and need different practice.

Anatomy knowledge comes from study: books, 3D references, dissection diagrams. This is intellectual knowledge.

Anatomy application comes from drawing: gesture practice, figure studies from life or reference, construction exercises. This is motor memory and spatial understanding.

Most people spend their study time acquiring knowledge and then wonder why their drawings don't improve. The application practice is where the change happens. You can know exactly what a deltoid looks like in anatomy terms and still not be able to draw it convincingly because you haven't built the motor memory for rendering its form.

My recommendation: for every hour of study, spend two hours drawing from reference specifically focusing on the structure you studied. The ratio matters. Knowledge without application doesn't transfer to the page.