With these patches, things build and seems to work. Have fun.
/Sune
diff -Nru fraqtive-0.4.8/debian/changelog fraqtive-0.4.8/debian/changelog
--- fraqtive-0.4.8/debian/changelog 2018-03-15 14:34:14.000000000 +0100
+++ fraqtive-0.4.8/debian/changelog 2018-08-15 11:34:18.000000000 +0200
@@ -1,3 +1,10 @@
+fraqtive (0.4.8-6.1) UNRELEASED; urgency=medium
+
+ * Non-maintainer upload.
+ * Qt5
+
+ -- Sune Vuorela <[email protected]> Wed, 15 Aug 2018 11:34:18 +0200
+
fraqtive (0.4.8-6) unstable; urgency=medium
* Set a save URL in the homepage field.
diff -Nru fraqtive-0.4.8/debian/control fraqtive-0.4.8/debian/control
--- fraqtive-0.4.8/debian/control 2018-03-15 14:34:14.000000000 +0100
+++ fraqtive-0.4.8/debian/control 2018-08-15 10:58:36.000000000 +0200
@@ -17,8 +17,7 @@
libglu1-mesa-dev,
libgl1-mesa-dev,
libpcre3-dev,
- libqt4-dev,
- libqt4-opengl-dev
+ qtbase5-dev
Standards-Version: 4.1.3
Package: fraqtive
diff -Nru fraqtive-0.4.8/debian/patches/fixinludes fraqtive-0.4.8/debian/patches/fixinludes
--- fraqtive-0.4.8/debian/patches/fixinludes 1970-01-01 01:00:00.000000000 +0100
+++ fraqtive-0.4.8/debian/patches/fixinludes 2018-08-15 11:34:18.000000000 +0200
@@ -0,0 +1,29 @@
+Description: Add missing includes
+ Qt5 has had a bit of includes cleanups. Apply those.
+Author: Sune Vuorela <[email protected]>
+
+---
+Origin: other
+Forwarded: no
+Last-Update: 2018-08-15
+
+--- fraqtive-0.4.8.orig/src/configurationdata.cpp
++++ fraqtive-0.4.8/src/configurationdata.cpp
+@@ -27,6 +27,7 @@
+
+ #include <QDir>
+ #include <cstdlib>
++#include <QDataStream>
+
+ ConfigurationData::ConfigurationData()
+ {
+--- fraqtive-0.4.8.orig/src/fractalgenerator.h
++++ fraqtive-0.4.8/src/fractalgenerator.h
+@@ -22,6 +22,7 @@
+ #include <QEvent>
+ #include <QMutex>
+ #include <QWaitCondition>
++#include <QObject>
+
+ #include "abstractjobprovider.h"
+ #include "datastructures.h"
diff -Nru fraqtive-0.4.8/debian/patches/series fraqtive-0.4.8/debian/patches/series
--- fraqtive-0.4.8/debian/patches/series 2018-03-15 14:34:14.000000000 +0100
+++ fraqtive-0.4.8/debian/patches/series 2018-08-15 11:27:50.000000000 +0200
@@ -1,2 +1,4 @@
01-desktop-keywords.diff
02-spelling-error.diff
+Use-Qt5
+fixinludes
diff -Nru fraqtive-0.4.8/debian/patches/Use-Qt5 fraqtive-0.4.8/debian/patches/Use-Qt5
--- fraqtive-0.4.8/debian/patches/Use-Qt5 1970-01-01 01:00:00.000000000 +0100
+++ fraqtive-0.4.8/debian/patches/Use-Qt5 2018-08-15 11:34:18.000000000 +0200
@@ -0,0 +1,18 @@
+Description: Fix bulid system to use Qt5 instead of Qt4
+Author: Sune Vuorela <[email protected]>
+
+---
+Origin: other
+Last-Update: 2018-08-15
+
+--- fraqtive-0.4.8.orig/configure
++++ fraqtive-0.4.8/configure
+@@ -81,7 +81,7 @@ for i in $paths; do
+ if test "$version" != "**Unknown**"; then
+ major=`echo $version | sed -e "s/\([0-9][0-9]*\).*/\1/"`
+ minor=`echo $version | sed -e "s/[0-9][0-9]*\.\([0-9][0-9]*\).*/\1/"`
+- if test $major -eq 4 -a $minor -ge 3; then
++ if test $major -eq 5 -a $minor -ge 3; then
+ QMAKE=$i
+ break
+ fi
