The Android 5.1 Lollipop update has been released for Verizon HTC One M9 in mid August 2015, it’s a little behind other major US variants that have got it first. Just like before the update is available via OTA and you can download and then apply the update directly on the phone, but this procedure only for those who are still running the stock unrooted HTC Sense ROM without any major modifications into the systems.
The standard official OTA update installation procedure doesn’t apply to a device with custom recovery (TWRP) or running a custom ROM installed. You may be able to download the Android 5.1 OTA file for Verizon HTC One M9, but you will have problems when make an attempt install it. As we know, to gain root access on this device you need a custom recovery like TWRP, while the stock OTA update can only be installed using stock recovery. So you need a stock recovery from previous firmware (Android 5.0.1) to flash an official Android 5.1 OTA.
There is an easier way to upgrade HTC device, using an RUU. Unfortunately, when this article was written, the Android 5.1 RUU is not yet available for Verizon HTC One M9. There is only the stock of official OTA package, which can only be used if your device running stock systems (unmodified system, bloatware and stock recovery to flash it).
You can also choose to install a custom firmware based on 5.1 OTA via fastboot flash, it’s also include a TWRP Recovery 188.8.131.52. You can get these resources directly from xda thread by dottat.
The Android 5.1 update for Verizon HTC One M9 brings several enhancements in addition to the core OS upgrade, some of which are:
- Factory reset protection: Lost devices will stay locked, even from factory reset. You need to sign in into a Google Account to unlock it
- Enabling LTE roaming
- Google Wallet now pre-loaded
- Video calling now enabled
- Numerous Android Security Patch like stagefright vulnerability.