On Windows, FX gets the list of fonts to use to build a fall back
list for a composite font from the windows linked font list.
This is historically focused on CJK fonts and so if you need
something else, such as Indic or special symbols, you may
get missing glyphs. Prior to JDK 11, we could rely on adding the
JDK's Lucida Sans font to get around most of that, but it is not
there any more, leading to https://bugs.openjdk.java.net/browse/JDK-8215799
There's something of a workaround in the font code where
the code path for complex text layout dynamically adds whatever DirectWrite finds as a fall back and that is used in fixing that bug - needed because prior to fixing that, the webkit code was first directly checking if a code point was supported and not trying to render it, which is what triggers the dynamic addition.

And TextLayout won't help if it is symbols or something that don't trigger this undocumented side effect anyway.

So I think we need to look at creating a fuller list of system fonts with broader coverage to be added to the fallback list for
the FX composite fonts.