>> I may add that usage of XDG_CURRENT_DESKTOP environment variable is broken
>> now in KDE applications from Sid, and because of it they look very ugly when
>> launched outside plasmashell or via `ssh -X ..`.
>>
>> For example, dolphin lacks all file icons and icons at toolbar and menus.
>> Plus it uses some strange theme (not breeze).
>
> Dolpin looks normal in my install.
Have you tried to launch it in openbox session or via ssh?
`export XDG_CURRENT_DESKTOP=KDE` for applying proper Qt settings does now work
anymore.
Best wishes,
Boris