I am running Linux Mint 21 Cinnamon and mean to remember that I have played around with some settings to make the application windows default font size larger, but running now the systemsettings shows somehow zero 0 items in the section Appearance.
The problem I have is that all KDE applications look ugly because of double spaced text lines and in some of the dialog boxes I can't reach the OK buttons because the vertical box sizes exceed 1080 pixels of the used display.
See the images below for what I am speaking about.
Any idea how can I change the line spacing to a default one without an extra empty line between the text lines?
UPDATE answering question asked in the comments:
Default after fresh installation of KWrite was the Chandas font and the double spacing of lines occurs in the editing area too:
After changing the font to Liberation Mono the double spacing of lines in the text editing area was gone, but was still there separating the toolbar from the menu by one line with the underlines in Menu texts (and with double spacing of lines in the Settings dialog boxes too):



