@Mijikai
Glad my explanation helped. It's not the official explanation, it's my experience talking. I could be wrong!
Regarding the qt5-default issue, I'm using the gtk dependencies so I'm not having that problem. I can't tell you what is happening, but "maybe" if you installed the gtk and the qt dependencies there is some clash of interest? I'm just guessing?
Regarding the .desktop file, and I do tend to be a bit unconventional, but below is what mine has in it. Bear in mind I didn't use the PB installer so I had to create the .desktop file myself, and put everything where I wanted it, and get it all working. Did I mention I was unconventional?
[Desktop Entry]
Categories=Development;
Comment[en_GB]=PB IDE
Comment=PB IDE
Exec=/home/user/.local/bin/PB-611/compilers/purebasic
GenericName[en_GB]=
GenericName=
Icon=/usr/share/icons/pb.svg
MimeType=
Name[en_GB]=PureBasic611
Name=PureBasic611
Path=
StartupNotify=true
Terminal=false
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=
X-KDE-SubstituteUID=false
X-KDE-Username=
Exec= is pointing to the actual location of the PB compiler on my system.
Icon= points to the icon on my system.
You will usually find the real PB icon in the top level PB folder and it's called logo.png, so point yours there.
Looks like this on my system. I'm using the BeautyLine icon theme and I custom made the PB one.
Moulder.