The guide is now considered to be fully-functional and ready for use by anyone! Do not be afraid of looking up other guides if you ever feel that this guide lacks any details, however. 🙂 The risk of bricking is somewhat low: Even if you do end up with no Android version on your phone, you can still use the recovery environment(s) and the phone’s bootloader to remedy the issue in some or another way. If you do somehow brick it, however, I am not responsible for anything bad that do/has/will occur (nor for any of the faults that the phone manufacturers have committed).
There are twenty fantasillion guides out there on how to install custom updates on your Android phone. You’ve heard talk everywhere about them. Cyanogenmod, Ubuntu Touch, LineageOS, SailfishOS, or just a promise to install a new Android version that your phone manufacturer (or in rare cases your cellular service) couldn’t be arsed to send out to you. And then you look up guides on how to do it, and you quickly realize that the guides omit vital details, fail to cover entire chunks of the process, and are written by such stuck-up nerds that they assume that you already know all this stuff.
Therefore I will write a summary on how to do it, the right way. This has been tested with LineageOS 14.1 (a vendor-edited version of Android 7.1) on my own Lenovo Vibe K5 (A6020a40 system structure), on the 4th of June 2017, as well as Cyanogenmod 11 on an HTC Wildfire S. I see no reason why this wouldn’t work with other phones too, although some differences may occur for users of Samsung phones and other smug brands, as they’re notorious for changing vital Android system functions to their own liking. Let’s delve into this, shall we?