The attached patch I found here enables infix search for search box suggestions for page names, which is a very nice enhancement and it would be great if this functionality was incorporated into the extension.
It looks like there have been an attempt to introduce this to the extension but was abandoned and no ticket was created for it.
I have just configured SphinxSearch in the following set-up:
MediaWiki 1.27.3 sphinx-2.2.11-release SphinxSearch 0.9.0
and it appears to be working fine.