Source (link to git-repo or to original if based on someone elses unmodified work): https://github.com/Fausto-Korpsvart/WhiteSur-kde/tree/master/aurorae
Big Sur Aurorae
This is a modification based on vinceliuice's theme, WhiteSur-kde.
Basically, what I've done are a few modifications for the Aurorae White Sur window decoration theme, for white and dark versions, it seems a bit more like the original version of macOS Big Sur, since the original versions of the Aurorae theme, of the White Sur themes, are quite thin and don't look very good and, in my opinion, I think it looks a bit strange and it doesn't look much like the original macOS decoration so I took the liberty of making small modifications to Vinceliuice's original themes to make it a little more like the original macOS on his White Sur themes.
You will see the clear difference, I hope you like these improvements.
The best option to install "Aurorae" themes is open the "System Settings" of KDE Plasma, then enter the "Application Style" section, then "Window Decoration" and at the bottom right, click on "Get New Window Decoration", then do a search for "Big Sur Aurorae" and then click on "Install".
The second option is download the files from Big Sur Aurorae themes then unzip the files and move them to the path: "/home/yourUserHere/.local/share/aurorae/themes/", and to apply it go to "System Settings", "Application Style", "Window Decoration", search the theme and click on **"Apply"**
I hope you like the small modifications made, enjoy them };-]!!!