HTC is one of the few OEMs that make it easy to unlock the bootloader on their devices. And while they do warn you that doing so voids your warranty, they don't tell you that it also prevents you from collecting promotions that come with their devices.
It was recently announced that all HTC One owners would be eligible for free cloud storage, but seeing as having an unlocked bootloader prevented that promotion from being redeemed, most of us were left out in the cold. But as the old saying goes, "A closed mouth doesn't get fed."
I went ahead and contacted HTC support, and sure enough, a few days later I was the proud owner of 100 GB of free Google Drive storage (for two years, anyway).
Before starting out, you are going to need to locate your IMEI number, which will be on the original box your device came in, or can be located through Settings -> About -> Phone identity -> IMEI.
When you have it, head over to the HTC customer support page and enter your device information into the form. In the message section, let them know that the HTC Drive offer is not being recognized by your device. You can also use HTC Live Chat, but it isn't available 24/7/365.
Once the ticket has been processed, you will receive an email letting you know that a rep will be looking into your case. It took HTC about a day to generate the link I needed to claim my free storage, but after following the link, the cloud space was immediately credited to my account.
This will work for every HTC One out there, so if you own multiple devices, don't be afraid to let them know you want what is rightfully yours, even if you did everything in your power to trick out your phone.