Hi Gino, when you change the default kde between dark and light it saves this info inside /home/username/.config so I basically switched back to light theme and duplicate the config folder as .config-light and switched back to dark theme. Then using the above command from previous post I told enpass to use the light themed environment.
But out of curiosity, why aren't you using the enpass 6? I'm not using Linux right now but I thought it was released on both platforms.