Open type fonts

My understanding is that OpenType should work fine, but there are certain specific fonts with issues, also certain ways of installing fonts (user vs system) that cause problems. See #280244: User fonts not visible to MuseScore 3 (Windows 10)

FreeSerif is an OpenType font with a full set of ligatures, but MuseScore doesn't seem to support OpenType feature sets at all. I've attached a few images, one of the word Affettuoso set in MuseScore, and one with the same word (and a few others) set in Illustrator, in FreeSerif Bold Italic. This is a real problem, as without the ligature substitution for "ff", Affettuoso looks just awful.

It seems ligatures are only a problem with FreeSerif — which is weird, because the ligatures work in other programs. I tested other OTFs in MuseScore, and all seem to work fine (Bulmer, Adobe Garamond, Adobe Caslon, Newstyle). I recompiled the feature sets in the entire FreeSerif family and exported new versions of these fonts, but MuseScore still does not make the correct substitutions. Could this be a clue to what is going on?

A theory: FreeSerif has glyphs, kerning pairs and features for several languages (including Armenian, Georgian, Cherokee and Thai), and it is possible it is too complex for MuseScore to handle. It used to be that when Microsoft Word encountered a font with more than 500 kerning pairs, it simply ignored kerning altogether. Is something like this what is happening with FreeSerif and MuseScore? It's got too much code, so it's ignoring some of it?