It will probably be simplest to just use FreeType on Android,
too. (Android uses it itself, but doesn't provide its API publicly.)

Probably fontconfig, too, although there shouldn't be much
configuration per se that a LibreOffice-baed app would have to do at
run-time; it will have to bundle all fonts it is going to use anyway,
I think, so all font information is known a priori. But maybe in the
future there will be user-installable system fonts on Android, or
something.