XeTeX as default output format has vanished in 2.4

[Anthony Ashmore]

Hello everyone!

I have a quick question regarding the change from 2.3 to 2.4. In 2.3, I 
have a number of files that use custom fonts via a \setsansfont command 
in the preamble, together with a local path to the font. I have been 
compiling these successfully by leaving "Fonts -> Use non-TeX fonts" 
*unchecked* and then setting "Format -> Default output format" to "PDF 
(XeTeX)".

However, in 2.4, the option to default to XeTeX has vanished unless you 
set "Use non-TeX fonts" to true. It also seems I cannot just go to "File 
-> Export" and select "PDF (XeTeX)" from there (it is greyed out). If I 
check "Use non-TeX fonts", 2.4 seems to go out of its way to redefine 
the math font, causing me endless headaches.

Is there any way to re-enable this?

Thanks very much!