What Free Software font subsetter should one use these days to get a subset .ttf given a .ttf and a list of characters such that the subset font retains not only the primary glyphs for those characters but also alternative glyphs and ligatures whose participants are on the list?
I’d use FontForge manually if this was a one-off, and otherwise write a script that manually parses the OTF data. Not a great answer, I know :(