These AppImages were built and tested on a Linux Mint 19.
They were built using https://github.com/AppImage/AppImages.git running
bash -ex ./pkg2appimage recipes/kicad4.yml
or
bash -ex ./pkg2appimage recipes/kicad5.yml
using the Yaml files from the recipes folder.
Feel free to use the recipe for the nightly version.
Please see releases for all the binary AppImages for download.