https://www.musical-u.com/learn/how-to-tune-your-guitar-by-ear/
A lot of discussion can be had over whether the guitar should be tuned by ear or with the help of an electronic device. In times of desperate need, when all your digital tuners have died slow deaths, all you have to rely on are your hands and your ears! Fortunately you can tune your guitar perfectly with just these. https://www.musical-u.com/learn/how-to-tune-your-guitar-by-ear/