Bip39 Trezor. From this level ahead the seed may very well be written on paper or spoken more than phone which opened up new, physical means of backing up the seed (several paper copies in different spots, durable copies on metallic plates with added security from hearth/flood and so forth.). https://thebookpage.com/story4382085/seed-for-the-random-number-generator-5-simple-statements-about-bip39-word-list-github-explained