Mobile vendors not regularly update Android mobile operating systems. Make available a new version of Android for mobiles will take too much time. Therefore mobile users are not able to experience the features of the latest Android version and security updates. Mobile vendors do not release updates for the old devices, and they concentrate on releasing new models.
AOSP (Android Open Source Project) regularly release updates and new versions. But users are not lucky to receive the latest releases of Android new versions on old devices. Android Project introduced Project Treble to speed up the distribution of new releases. Android Project releases new versions, and the mobile phone vendors make changes to suitable for the hardware. This process requires too much workforce, and frequent updates from vendors are not possible. With the introduction of Project Treble, users can install Android latest version on their devices. Project Treble Android image can install on compatible mobile hardware same like installing an Ubuntu Linux on any computer. All mobile phones preloaded with Android Oreo (Android 8.0) at the time of purchasing is suitable for the Treble project. It means that the mobile user can download and install a Project Treble image of the Android operating system. The mobile users can check the Treble compatibility using the following app; they can be download from Google Play Store.
Users can find various generic system image (GSI) suitable to install on Treble supported mobile devices irrespective of hardware type. Android GSI images are appropriate to fit in any Treble supported mobile phones.
Lot of Android custom ROMs in GSI format. One of the leading GSI AOSP project by phhusson. He regularly releases GSI images of the latest versions of Android operating systems. GSI images by Phhusson are unmodified Android; users can experience pure Android experience. It does not contain any customisations and beautifications usually available with stock Android available with new mobiles. For example, Xiaomi mobile company customise the ROM and add beautifications and other changes. They also add apps not desired by the users (bloatware). It makes the vendor ROM heavy and noisy. GSI image of phhusson contain an only base version of Android, and users can add required apps later. AOSP GSI images are run smooth and provide good battery life.
Users can find GSI images of other custom ROMS. Lineage OS, Arrow OS, Havoc OS, CrDroid, AospExtended etc. are the popular custom ROMs. Most of the GSI images of custom ROMs build on phhusson project. Here is the list of custom ROMs based on phhusson.
https://github.com/phhusson/treble_experimentations/wiki/Generic-System-Image-%28GSI%29-list
Here is a detailed article on how to install a GSI image on a mobile a Treble supported phone.
