"Lognko" (odd as it looks) brings up a number of results, too. I don't
know for sure, but I'd be willing to bet that there isn't a strongly
standardized spelling system for the Mapuche/Mapuce language.
No, there isn't, but the sound in question does seem to be the one that
occurs twice in "singing", and I don't see why anyone would want to write
that gn.