/usr/share/lyx/kbd/greek.kmap is in lyx-common 2.2.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | # Greek keyboard definition for LyX - hopefully correct #
# Flames to Alkis Polyzotis, alkis@dbnet.ece.ntua.gr
#
\kmod ; acute aeioyvhAEIOYVH # αειουωΑΕΙΟΥΩ
\kmod : umlaut iyIY # ιυΙΥ
\kmod ' grave ayiAYI
\kmap Q :
\kcomb acute umlaut iy
\kcomb umlaut acute iy
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