Xnybre's Scientific Keymap was initially based on the US keymap. Ignoring Alt Gr and and Alt²Gr everything is still like the normal US keyboard layout (except for the Caps Lock key, which is useless anyway). The primary idea was to make a keymap useful for programming (like the US layout) but with better positions for the Danish letters than the US International layout.
After this, I added letters for more languages, as well as a number of dead keys to enable the input of more national letters.
Later, a lot of other symbols were added like the entire Greek alphabet and various mathematical symbols.
The right Alt key is used for Alt Gr and the Menu key for Alt²Gr (Ctrl+Alt²Gr should work as Menu).
XSK for X/Wayland (used with Linux)
|None||Alt Gr||Alt²Gr||Alt Gr + Alt²Gr|