I‘ve bought a ten less US layout qwerty keyboard (Keychron K3) for my programming work. There is a neat feature on macOS to type ‘Umlaute’. Just long press vowels and you can choose from all possible variations of the vowel. I’ve also build a custom Helidox Corne keyboard, but couldn’t learn the new typing system… (https://thomasbaart.nl/2018/11/26/corne-keyboard-helidox-bui...)