At the moment, Google’s Android L Preview Builds supports only the Nexus 5 and the Nexus 7 devices officially, but thanks to ssrij an XDA Developers senior member an unofficial port for HTC One M7 handset has been produced. Because kernel and ramdisk modifications were performed to adapt Android L on the HTC One M7, it is possible that the smartphone will not run like you would expect it to.
However, now you can get Android L on your HTC One M7 device in an early stage, meaning that you can get a taste of Android L with some caveats such as WiFi, the camera, Bluetooth, sound and data. But, most of the features are working in this port and the issues are expected to be fixed soon.
Therefore, the ROM currently is a way to try Android L on your HTC One M7 smartphone, but knowing that this ROM does not work for everyday functionality.
So, if you are determined to try it, the installation is really simple, at least if you already have root access and recovery alternative in your HTC One M7. If yes it is just a matter of transferring the ROM as a zip file to the internal memory of your smartphone and attempt to install it through recovery. The guide and details of this process can be found here.
