Based on “the maintenance of a device or system … in order to make it work in accordance with its original specifications” can I or can I not legally unlock a device to use a different OS/apps on it?
I don't think so, FTA: "“I read it as the ability to reset to factory settings,” Nathan Proctor, head of consumer rights group US PIRG’s right to repair efforts, told me in an email. Although you could make an argument that the device never performed according to its specifications and your unlocking the device is merely an attempt to repair a fundamentally broken product, but that seems like it'd be a hard sell.
But it does create a gray market for the information obtained by people who legally break DRM for "repair and maintenance." Information set free can be used for anything, wink wink.