[Huawei P9 Guides, News, & Discussion] zgfg:
Yes, you don"t need to buy DC credit. I did a slightly different procedure to unlock my bootloader:

Step 1) Go to http://www.emui.com/en/plugin/hwdownload/download

click to Unlock Bootloader, login with your Huawei ID, fill the form (Serial Number, IMEI, Product ID - there are instructions how to read them), and you will immediately obtain passcode (16 digits) for unlocking the bootloader

Note 1: You can't open the EMUI plugin page from phone (blank page, nothing), but it works from PC (I was using Internet Explorer)

Note 2: At the beginning, you have to select your country but e.g. EU countries are not listed. I chose (default) Hong Kong instead, procedure was in English and everything worked fine

Note 3: If you don't have Huawei ID, you have an option to register for Huawei ID first. The whole procedure (registering for Huawei ID, filling the form to obtain passcode for unlocking bootloader) will take you 5-10 minutes

Note 4: Actually, I did have Huawei ID that I had previously registered through HiCare app on the phone. But back then, in HiCare app, I chose my real EU country (to register for warranty). It did not allow me to use that Huawei ID here for the bootloader passcode form, saying that my Huawei ID was registered in different country (EU countries not offered on the EMUI page). Hence I registered for a new Huawei ID (as from Hong Kong), associated with my another e-mail address, and used that Huawei ID for unlocking the bootloader form

Step 2) Instead of using manual commands to unlock the bootloader, you can use SRK Tool from https://xdaforums.com/p9/development/tool-srk-tool-huawei-bootloader-root-t3374068

There is a download link and short video (watch it carefully) how to use the SRK Tool. SRK Tool will guide you through the unlocking bootloader process

Note 5: In SRK Tool, you can choose fastboot or USB debugging techniques. I opted for USB debugging. In that case you don't need ADB drivers and you don't need to boot the phone to fastboot

Note 6: For USB debugging option, SRK Tool needs HiSuite on the PC. If you don't have HiSuite installed on the PC, SRK Tool will automatically install HiSuite and all its drivers. You may need to attempt twice to unlock the bootloader, first attempt will fail but SRK Tool will install HiSuite and drivers, second attempt will succeed

Warning: Don't attempt to install TWRP or root to Nougat from SRK Tool - its TWRP and root are outdated and good only for Marshmallow, you could brick the Nougat

Final remarks:

No matter how you unlocked the bootloader (by DC Unlock, through SRK Tool or manually by fastboot), it will factory reset the phone and you will have to setup/install everything as on the brand new phone (there are options to clone previous installation through Google account or to restore through HiSuite).

Don't worry, factory resetting keeps the previously upgraded e.g. my c432 b378 (EMUI 5.0 and Android 7.0)

Once the bootloader is unlocked (no matter how you did), every time you boot it will display a warning that phone is not secure. You can not avoid this annoying warning unless you re-lock the bootloader (by fastboot or by SRK Tool again - in any case, save your 16 digits bootloader passcode). But if you re-lock the bootloader, phone will factory reset again, and you will loose TWRP, root, etc

Upon factory resetting and with the bootloader unlocked, I didn't try HiCare app anymore (I don"t want to risk loosing my warranty)

I was using Windows 7 and everything worked fine but I had to disable virus protection - it was finding SRK Tool unsafe (as well as ADB drivers and fastboot setup that I had also downloaded) and repeatedly deleting them from the PC