Recoll is not just a desktop search engine, it can also be used as an intranet search engine either 'stand-alone' [1] or as an 'engine' in Searx [2]. I made the Searx engine a few years ago to extend Searx to intranet search, the QT qui is not used (an, on Debian, not even installed - only the 'recollcmd' package is needed).

[1] https://github.com/koniu/recoll-webui

[2] https://github.com/searx/searx/pull/1257