KaiOS
Developed in 2017, KaiOS is a mobile operating system designed for inexpensive cell phones with no touch screen capabilities. The software is based on the open-source Firefox OS (operating system) project. It allows apps developed for touch screen operating systems, like iOS and Android, to also run on button-operated hardware found in flip phones or other traditional form factors. KaiOS apps are controlled using the keypad, or vocally via the Google Assistant, which is supported in the operating system.
KaiOS is available in several popular legacy and budget cell phone brands, including Nokia, Cat, Energizer, and Alcatel. Smartphone apps ported to KaiOS are available to download in the KaiStore, and include Google Duo, Facebook, Whatsapp, and Google Maps.