This Repository can be added to your system manually by copying the lines below and adding them to your system's software sources.
wget -qO- https://archive.darkgrave.de/dgrepo-archive-keyring.gpg | sudo tee /etc/apt/trusted.gpg.d/dgrepo-archive-keyring.gpg
sudo add-apt-repository "deb https://archive.darkgrave.de/unity/ YOUR_UBUNTU_VERSION_HERE main"
sudo apt update