How can I determine which installed fonts can display a certain glyph?

Given a glyph (eg: '👌'), how do I determine which (if any!) fonts contain it?

That particular glyph displays in firefox, so presumably it's on my system, but I've not been able to get it displayed in a python-generated pdf.

Try gucharmap. You can search for a given character (say, ã), and also dynamically change the font used to display that character (e.g. Liberation Sans to something else).

Try landroni's answer, but with the advent of WebFonts, there is no guarantee that any particular font or glyph is going to be resident on your system if you only see the glyph rendered on webpages. You can use the Web Developer Tools (Tools->Web Developer->Inspector) in Firefox to inspect the contents of a webpage to see if WebFonts are being used.