Ethiopian support is a work in progress. See Ethiopian Setup.
et keyboard is in the xkeyboard-config package, already in our builds.
Please note that there may be additions to the Ethiopic characters in the Unicode standard in the coming years, as more linguistic work is done.
This document contains some information about Ethiopic
There is a mention of Ethiopic on pages 4 and 5 of this document.
There are code charts for three blocks of Ethiopic characters.