1. Android -
Windows Mobile is a discontinued mobile operating system developed by Microsoft. It was primarily used on devices made by Microsoft and its partners, but it never gained significant traction in the market
BlackBerry OS was the operating system developed by BlackBerry for its smartphones. It was known for its focus on security and productivity features.
Tizen is an open-source operating system developed by Samsung and others. It is used primarily on Samsung's own devices, such as the Samsung Galaxy Watch.
Ubuntu Touch is an open-source operating system developed by Canonical for smartphones and tablets.
Sailfish OS is a Linux-based operating system developed by Jolla. It is used primarily on Jolla's own devices, but it is also available on other smartphones and tablets.
KaiOS is a mobile operating system developed by KaiOS Technologies. It is designed to run on low-cost feature phones and is known for its simple user interface and support for popular apps like WhatsApp and Google Maps.
HarmonyOS is an operating system developed by Huawei. It is designed to work on a variety of devices, including smartphones, tablets, smartwatches, and smart home devices, and is known for its security features and ability to seamlessly switch between devices.