Download the deb for xenial from here: https://packagecloud.io/Flirc/repo/packages/ubuntu/xenial/flirc_3.9.7_amd64.deb
install:
sudo dpkg -i /path/to/downloaded/flirc_3.9.7_amd64.deb
sudo apt install -f
There was a package that I needed the i386 version of but I can't remember which one. The error messages from installing led me in the right direction.