20.04 Configure Error: The important program KDE-Config was not found

NDISWrapper by itself is available in official Ubuntu repositories. To install it use commands below:

sudo add-apt-repository universe
sudo apt-get update
sudo apt-get install ndiswrapper # ndiswrapper-dkms

Then about KNDISWrapper KDE front-end.
It is available only on ArchLinux. The relevant package was last updated in 2015-2017. To compile it on Ubuntu 20.04 LTS (focal fossa) use commands below:

sudo apt-get install git build-essential qt5-default qttools5-dev-tools

cd ~/Downloads
git clone https://github.com/maz-1/kndiswrapper.git
cd kndiswrapper/
mkdir -p build
cd build
qmake ..
make
cd ..
cp -r translations ./build/
lrelease ./build/translations/*.ts

sudo mkdir -p /usr/local/share/{kndiswrapper,applications,pixmaps}
sudo mkdir -p /usr/local/bin

sudo cp "./icons/kndiswrapper.svg" "/usr/local/share/kndiswrapper/kndiswrapper.svg"
sudo cp "./icons/kndiswrapper.svg" "/usr/local/share/pixmaps/kndiswrapper.svg"
sudo cp build/kndiswrapper /usr/local/bin
sudo chmod 755 "/usr/local/bin/kndiswrapper"
sudo cp "./build/translations/"*.qm "/usr/local/share/kndiswrapper"
sudo cp "./build/translations/cards_known_to_work.txt" "/usr/local/share/kndiswrapper"

and finally create desktop-icon file for it using long single command below

cat <<EOF | sudo tee "/usr/local/share/applications/kndiswrapper.desktop"
[Desktop Entry]
Encoding=UTF-8
Name=kndiswrapper
Name[de]=kndiswrapper
GenericName=kndiswrapper
GenericName[de]=kndiswrapper
Comment=A GUI for ndiswrapper
Comment[de]=Eine GUI fuer ndiswrapper.
Exec=kndiswrapper
Icon=kndiswrapper
Terminal=false
Type=Application
StartupNotify=true
Categories=Network;
EOF

and then find icon in applications menu/dash.