Sigil is, as far as I read (since I've never use it), tied only to EPUB format. TeX can be compiled and converted to multiple formats. To make an EPUB one just

Sigil is, as far as I read (since I've never use it), tied only to EPUB format. TeX can be compiled and converted to multiple formats. To make an EPUB one just need to create appropriate sructure and opf/xml, then pack it.