pacman -S plasma xorg

systemctl enable --now sddm

That's actually it. Check out all the KDE software and suggested packages below and install whatever you like.

Just add the packages to the above pacman command.

networkmanager-openvpn wireguard-tools keepassxc arch-audit konsole keditbookmarks gparted htop dolphin spectacle wget lm_sensors ark kleopatra kate kompare rsync

pulseaudio pulseaudio-alsa

vlc openshot gimp inkscape

thunderbird thunderbird-i18n-en-us wqy-zenhei ttf-liberation libreoffice-fresh cups cups-pdf xsane system-config-printer kdeconnect firefox okular gwenview

If you install cups you also need to enable the service:

systemctl enable --now cups.service

bash-completion cronie

Add for bash-complition the following to your .bashrc:

echo "if [ -f /etc/bash_completion ]; then          
. /etc/bash_completion
fi" >> ~/.bashrc

Enable service for cronie:

systemctl enable --now cronie.service

Check also crontab.