ppa:lightzone-team/lightzone only appears to contain the package lightzone, and AFAIK the new add-apt-repository command updates source automatically, so these are the full commands:
sudo apt install software-properties-common
sudo add-apt-repository ppa:lightzone-team/lightzone
sudo apt install lightzone
The solution is mentioned by @Sysadmin. I adding further detail for ease understanding.
The fonts are stored in /usr/share/fonts folder. Just open this folder as administrator and copy-paste all eh fonts you downloaded in respective folders such as OpenType, TrueType and extract the files if it is in zip.
After this, the fonts will be available in all ...