OneOS

OneOS runs a second Android system next to One UI on a rooted Samsung Galaxy and switches between the two without flashing anything. One UI stays installed; the other system lives in a folder on the phone and starts on One UI's kernel as a container. Switch from the OneOS app, and come back with Back to One UI or by holding Volume Up + Volume Down for 3 seconds.

Needs One UI 9 (Android 17) and root with KernelSU. The OneOS app downloads what each phone needs and updates itself.

This project mirrors the OneOS app releases and system images. Source code, issues and the full guide are on GitHub: https://github.com/fahadalijaved/OneOS

Experimental: it can break your phone's data. Back up your accounts and data first, and remove the screen lock before switching. Not supported by Samsung, Google or any phone maker.

OneOS started from OneLineage by WeWaffles and builds its system images with MysticGSI.