Fluent is a fork of Breeze widget style and decoration. Aimed to follow the latest Fluent Design specifications.
CAUTION: It's still in a very early stage.
To get rounded corners on all corners, use the KDE-Rounded-Corners KWin script. I'm planning to include it into the project later.
Current state:
The project uses the standard CMake buildsystem.
So for example, the whole compilation process could look like this:
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr ..
make
make install