Autostart with umlauts in american keyboad

Solution 1:

• To easily type international characters on a US american Querty keyboard, switch to the keyboard layout English US International with dead keys or English International with AltGr dead keys. These keyboard layouts allow for easy entry of international characters using a "dead key". Change/add or remove keyboard layout in "Settings" - "Keyboard", Input sources.
• If you are specifically looking for autostarting the xmodmap command, then put that program in your Startup Applications. In standard Ubuntu, search for "Startup Applications" to open the "Startup Application Preferences" dialog where you can add a startup program. To execute xmodmap systemwide, i.e. for all users and during log in, add the command in a script file in /etc/profile.d