One of the biggest draws to the XDA forums are the abundance of custom ROMs, kernels, and modifications available for it. With the release of Android Pie, developers are working hard to port the latest Android release from AOSP to their devices. Two major roadblocks must be overcome before custom development can really take off on our forums: bootloader unlocking and then porting a custom recovery. Without the former, there’s no point even considering modding your device which is why the community is upset with Huawei’s recent decision. Without the latter, it’s too risky for most users to mod their devices because you could end up making your device inoperable if you don’t have access to stock images. Custom recoveries, especially Team Win Recovery Project (TWRP), are crucial to custom development, which is why official TWRP support coming to the Xiaomi Mi Max 3 and HTC U12+ are a big deal in each respective community.
Now that TWRP support is here for both devices, development can safely begin. The kernel source code for the HTC U12+ is already available, but we’re still waiting on the kernel source code to drop for the Xiaomi Mi Max 3. Since Xiaomi released the Mi Max 3 just last month, we should see the source code under the “nitrogen” branch pop up soon. Regardless, thanks to the plethora of similar devices that Xiaomi releases, don’t be surprised if ports using BLOBs from other Xiaomi devices pop up. And thanks to Project Treble support, you should be able to flash a GSI based on AOSP Android 8.1 Oreo or even the “semi-GSI” based on the Google Pixel‘s Android Pie system image. As for custom ROM support on the HTC U12+, the limiting factor on that is its popularity: We’re not sure there are many developers who bought the device. Keep an eye out on our forums, though.
Sideload the TWRP installer script: adb sideload name_of_twrp_installer_script.zip
The easiest way to stay up to date with the latest version of the custom recovery is to download and install the official app from the Google Play Store. If you’re rooted, it can patch the boot image automatically with the latest version. Otherwise, it’ll download what you need to install the latest version from the recovery/fastboot.