Use of libproxy leads to crash due to mixing Qt4 and Qt5 by that library

libproxy support was introduced as part of QTBUG-26295 ans it was for years known to cause issues due to (most likely) trying to pull Qt4 (probably to use KDE4 settings), see:
https://bugs.kde.org/show_bug.cgi?id=323407

I've recently got several similar reports for Otter Browser, from Linux and BSD systems, example from OpenBSD (in this case user claims to not use KDE4):
https://gist.github.com/mulander/ef25ad07e15cbe8a00b8f9738abb8e7f

Usually that issue can be mitigated by nuking libproxy-kde, but separate package is not always available, meaning that users have to manually disable system proxy...

Original report seems to call for option to enable it in explicit way, but AFAIK currently it is picked up if found.

Any chance to do something about this? Such reports will start to accumulating since more distributions pick up new Qt versions (mine appears to not installing libproxy-kde by default, but some seem to do so)...

I've got suggestion to parse output of proxy command instead, but this is not feasible solution...