The most consistent way to type letters like ö ü ä ß € with an US Layout Keyboard: Setting the keyboard to "US International" on Windows + Mac + Linux (Gnome) the following shortcuts will work
-
ä: “ followed by a
-
ö: “ followed by o
-
ü: “ followed by u
-
ß: right alt + s
-
€ (Windows + Linux): right alt + 5
-
€ (macOS): right alt + shift + 2
Settings -> Time & Language -> Region & Language
- Click on English (United States)
- Select "Options"
- Select "Add a keyboard"
- Select "United States-International QWERTY
Settings -> Keyboard -> Text Input -> Input Sources -> Edit
use the + in the lower left corner and find „US International - PC“
gnome-control-center -> keyboard -> Input Sources
Use the + and select English (US, intl., with dead keys)