KaiOS is described as 'brings smartphone-like functionalities to affordable phones: the KaiStore for apps. Video calls over 4G. Mobile payments through NFC. Even dual-SIM support' and is a Operating System in the OS & Utilities category. There are more than 25 alternatives to KaiOS for a variety of platforms, including Linux, Android, Linux Mobile, Self-Hosted solutions and iPhone. Most alternatives are Operating Systems and Mobile Os. The best alternative is Android, which is both free and Open Source. Other great apps like KaiOS are Ubuntu Touch (Free, Open Source), Replicant (Free, Open Source), Plasma Mobile (Free, Open Source) and iOS (Free).
Ubuntu Touch is a mobile version of the Ubuntu operating system for mobile devices. It is adapted to run naturally in a mobile, touch-screen environment but is also capable of functioning as a desktop computer while in "desktop mode".
iOS is a mobile operating system developed by Apple Inc. and distributed exclusively for Apple hardware. It is the operating system that powers iPhone, iPod Touch, and formerly iPad. Each main version of iOS / iPhone OS has introduced a big, main feature of the new version.
MIUI is a stock and aftermarket firmware for smartphones and tablet computers based on Android. MIUI, developed by Xiaomi, includes various features such as theming support. It is updated every Friday based on the feedback from its test users.
postmarketOS (pmOS), is a touch-optimized, pre-configured Alpine Linux that can be installed on smartphones and other mobile devices. The project is at very early stages of development and is not usable for most users yet. We develop a sustainable mobile OS