I found two:
RouteConverter
==============
https://www.routeconverter.com/downloads/en
should do what you want. It says it knows 82 file formats that define
routes, tracks, flight logs etc and can convert any of threm into any
other. The list includes both ICG and KML.
Seems to be a free download but you'll need to install the Java runtime,
aka Java JRE but, annoyingly, its quite unclear on what Java version is
preferred.
GPSbabel
========
https://www.gpsbabel.org/index.html
which should also convert KML into IGC and IGC into KML. Its written in
C, so doesn't need any additional runtime support. and is also free
software.
Have fun and let us know which one you tried and if it did what you want.
--
Martin | martin at
Gregorie | gregorie dot org