Day/Night Switcher
store.kde.org
Available in both Plasma 6 (and >= 5.22).Your binary khameleon! A simple button that allows you to switch between two chosen Plasma Color Schemes. Not only day/night, but any scheme you want!Dead...

You can find and download the project from the KDE Store and from https://store.kde.org/p/1804745/

Hey guys,

Just wanted to tell you that Day/Night Switcher has been finally ported to Plasma 6. I couldn’t have done this with the interest by the community on the project’s continuation. Anyway, let us all enjoy it.

I am only posting this in the hopes that old users who moved to Plasma 6 may catch up on the news.

See you around, kids!