The macOS Keyboard Layout for Europeans, Coders and Translators. If you are looking for the offical layout, check out the release page and download v1.3.
Additionally, this repo contains a modified verison (v1.4) of the layout, where the superscript numbers are written by pressing SHIFT and the subscript numbers without pressing SHIFT.
This is a port of the EurKEY Keyboard layout, which features a QWERTY baseline layout (=good access to braces etc.) with quick access to commonly used accented characters and Umlauts.
Please report if you find any missing characters.
Copy the two files EurKEY.keylayout and EurKEY.icns to your library, either system-wide (/Library/Keyboard Layouts) or for your local user (~/Library/Keyboard Layouts).
The Layout itself is licensed under GPLv3. The EU flag icon is taken from Iconspedia, created by Alpak and licensed under CC.