This site hosts Debian packages for the CSL platform.
Recommended one-liner (adds the repo and installs csl-setup):
curl -fsSL https://apt-repo-99104a.gitlab.io/install.sh | sudo bash
sudo install -m 0644 -D public.gpg /usr/share/keyrings/csl-setup-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/csl-setup-archive-keyring.gpg] https://apt-repo-99104a.gitlab.io/debian stable main" | sudo tee /etc/apt/sources.list.d/csl-setup.list
sudo apt-get update && sudo apt-get install -y csl-setup