This is not the first time it's happening and I looked for a solution but didn't find one.
After full system update/upgrade, double click on files (dolphin) doesn't work.
click on mp3 files (dolphin) - VLC doesn't open automatically
click on pdf files (dolphin) - Okular doesn't open automatically
click on docx files (dolphin) - LibreOffice Writer doesn't open automatically
click on text files (dolphin) - I get error message: KDEInit could not launch '/usr/bin/kate'
FYI, All programs works from KDE Application Launcher
So, in order to open a text file, I need to launch kate from KDE Application Launcher
and drag-and-drop my text file to it.
It is really not convenient
Tried to reinstall dolphin - didn't work
$ inxi -F
Kernel: 4.14.130-1-MANJARO x86_64 bits: 64 Desktop: KDE Plasma 5.16.2