How to prevent font-conf from using a specific font for a certain language/charset?
 

I'm trying to prevent font-conf from using my default font (FreeSerif) for Hebrew characters.

Except for the Hebrew characters, I'd like FreeSerif to be used as my default font for all characters.

I read this manual for font-conf, and also the following questions/articles:

• How to match on charset?
• How to set font per Unicode range / codepoint in fontconfig?
• Configuring Per-Locale Font Selection with FontConfig
• Change Default Font for a Specific Language
• I stared into the fontconfig, and the fontconfig stared back at me

What I've tried so far, and it didn't work:

• Using the “lang” property to prepend my font of preference for Hebrew. It didn't work as intended, because if a sentence started with a non-Hebrew character then FreeSerif would be selected over the entire paragraph, despite that it may contain Hebrew characters.
• Removing the Hebrew characters directly from FreeSerif via fontforge. It didn't work quite well because my new version of FreeSerif had some weird spacing artifacts between the characters, I had no idea why and I just gave up.
• Removing the Hebrew charset range (U+0591 to U+05F4) from FreeSerif via font-conf's <match> pattern. It didn't work at all because font-conf says that “Expression doesn't take any effects for delete and delete_all” for properties like “lang” and “charset”.

Sadly there's no option to disable a range of character from a font on fontconfig.
I had edit FreeSerif directly and remove the Hebrew characters in order to force fontconfig to use my fall-back font for Hebrew.