The Cubox keymap is probably for an older Linux kernel and will need to be transcribed into the 'toml' format used now. There is a section in the wiki on creating custom keymaps. It needs to be updated to reference the toml format but the files you need to create and their locations are still correctly described. There are lots of existing keymaps in /usr/lib/udev/rc_keymaps/ to crib the toml format from.
Or the whole point of flirc is that you can program it to respond to any remote. If you install the config app on a PC it should take no more than 2 mins to map all the core Kodi functions to remote buttons.