The ability to boot a generic, AOSP-based system image on a compatible Android device is undoubtedly one of the best outcomes of Project Treble. Since the release of Android 8.0 Oreo, manufacturers seeking Google certification are required to test their devices for Treble compliance by booting this Generic System Image (GSI) and verify basic hardware functionality. Treble requires that devices launching with Android Oreo and above separate the vendor implementation such as the HALs, the software that the OS uses to communicate with the underlying hardware, from the Android OS framework, which is why it is theoretically possible to boot the latest version of Android on a legacy device without modifying the boot or vendor image.

The reality, however, is not that simple. Google further refined Project Treble’s requirements with Android 8.1 Oreo and Android 9 Pie by fully implementing the VNDK (Vendor Native Development Kit) and introducing CTS-on-GSI (Compatibility Test Suite on Generic System Image) tests. Nowadays, Android 8.x devices aren't even officially considered to be Project Treble compatible, as Google is focusing only on compatibility with Android Pie and above. When we are talking about devices like the Huawei Mate 9 or the OnePlus 5/5T, which originally launched with Android Nougat and subsequently received Treble support via system software updates, you can't simply flash Google's version of Android 11 GSIs on them and expect it to boot with everything working.

At this stage, finding a device-specific Android 11 custom ROM from our forums may sound like a better proposition, but XDA Recognized Developer phhusson is trying to tackle the situation from a different angle. Instead of modifying original vendor images, the developer has successfully tweaked Google's Android 11 GSIs by incorporating device-specific fixes. The resultant GSI built should boot on any Android device that supports Project Treble, which means most devices that launched with Android 8.0+.

Android 11 Custom GSI
Unofficial Android 11 GSI running on 22 different Android devices. Thanks to phhusson for the photo!

Below you can find the devices on which phhusson has successfully booted his custom Android 11 GSI:

If you’re the type of person who prefers to live on the bleeding edge, then you’ll be happy to know that the first pre-release version of "Phh-Treble", phhusson’s self-compiled custom GSI based on Android 11, is now up for grabs. Before flashing, you should determine your device variant using the Treble Info app linked below. Afterward, grab the appropriate build from the project’s GitHub release page and learn how to flash a GSI here.

Download Phh-Treble v300.a (Based on AOSP 11.0)

Since this is the first alpha build, a number of hardware features and software components are broken in this GSI. If you stumble across any issues, you can report them here. Nonetheless, it's great to see how modularizing the Android operating system makes it easier for manufacturers to push updates to the software, which in turn helps third-party developers extend the effective lifetime of older devices. If more OEMs start to follow in Samsung's footsteps regarding OS updates and continue updating the underlying vendor interface, the whole Android ecosystem should see good returns in the near future.

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