Since we finally got why, can you please mark the thread as solved using the "Topic Tools" button ? So other forum users may know an answer has been found :)

Wait wait wait... I just realised that my brain got haywire, they are not related to each other. Sorry !

Anyway: Removed the clucene dependency, used FTS5 from sqlite instead.

From the 5.9.0 change file in the qttools sources.

Ok, I thought that since Lucene is a text search engine, then there might be some overlap with pcre2.

Anyway, I can now see it (here indeed).

Anyway: Removed the clucene dependency, used FTS5 from sqlite instead.

From the 5.9.0 change file in the qttools sources.

Sure you may :)

Phew! :)

I greped through the dist folder in qtbase's sources for pcre and there were two entries in the 5.9.0 release: the removal of pcre and the addition of pcre2.

Ok, got it now. I must confess that I didn't know about the purpose of Lucene, hence I didn't initially see the link between Lucene and pcre2, but now it makes sense to me. Thanks, I learned something today. :)

I greped through the dist folder in qtbase's sources for pcre and there were two entries in the 5.9.0 release: the removal of pcre and the addition of pcre2.

I re-greped through all of the sources for lucene.

From a quick look, it has been replaced with pcre2.

Thanks @SGaist. May I ask where you saw this (I googled for Qt Lucene and couldn't find anything relevant) and from which version of Qt it got replaced?

From a quick look, it has been replaced with pcre2.

Completely unrelated, I've mixed things...

besides some (frustrating) GUI glitches (on macOS at least)

I am glad I haven't updated yet, thanks for pointing this out, would wait until Qt5.9.x release. I am happy to hear Qt team add some many new features into Qt, but I prefer stability more than quantity.