Do I need electronic shifting on an endurance bike?

Electronic shifting is not strictly necessary, but it is a significant quality-of-life upgrade for endurance riding. Shifting under load while climbing is smoother and more reliable with electronic systems, and the reduced hand effort matters when you are fatigued on hour five of a long ride. Shimano 105 Di2 and SRAM Rival eTap AXS have made electronic shifting accessible at lower price points. If your budget allows, it is worth the investment. Mechanical 105 is still excellent if electronic is out of reach.