ULS currently uses Gentium Plus version 1.510. This versions lacks all characters added in Unicode 7.0–13.0. The current version is 6.001 which adds these characters, fixes several glyphs (particularly diacritics in the Greek and Coptic block), and adds font feature settings for, among other things, capital adscript iota and porsonic circumflex in polytonic Greek.
Full release notes / version history: https://software.sil.org/gentium/history/
Download page: https://software.sil.org/gentium/download/