This is largely from the following gist. I'm pretty happy that it works this easily as it makes connecting to things much easier.
Enable multilib as you will need 32 bit libraries to use snx.
Update /etc/pacman.conf, uncommented the multilib header and Include:
[multilib]
Include = /etc/pacman.d/mirrorlist
Then update pacman:
sudo pacman -Syu
Now we can install the packages:
sudo pacman -Sy lib32-pam lib32-libx11 lib32-gcc-libs lib32-nss nss
Then we need something from the AUR:
paru lib32-libstdc++5
Download snx script.
chmod +x snx_install_linux30.sh
Install the script:
sudo ./snx_install_linux30.sh
With snx installed we can now use the Checkpoint VPN.
echo "password" | snx -s ip.add.ress -u username
To disconnect:
snx -d