/usr/share/kubuntu-default-settings/kf5-settings/jukrc is in kubuntu-settings-desktop 1:18.04ubuntu11.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | [MainWindow][Toolbar playToolBar]
IconSize=32
ToolButtonStyle=IconOnly
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