Any way to unlock the 5GHz WiFi band for US-version?

[PlaidRadish]

CONFIRMED - (BTV-W09 working 5G USA variant Nougat)

...The file to turn on 5Ghz wifi is called "cfg_btv_hisi.ini" and is in the "cust_spec\vendor\etc" directory ... just change "band_5g_enable=0" to "band_5g_enable=1" ... save ... enabling the permission change to write and then reboot...

I finally have my BTV-W09 working exactly how I want it:

• TWRP
• Magisk 20.3
• EMUI disabled
• Nova Launcher working as default
• Bluetooth working (formerly disabled with NRD90M test keys ROM)
• ... and now, 5G WiFi working, also!

...So, I wanted to just take a second to confirm that the location provided by @johje for USA BTV-W09 (I'm currently on W09C128B356) is exactly where I found the 5G enabler tag.
However, that location listed above is actually a shortcut.

The ACTUAL LOCATION for a BTV-W09,
running stock EMUI, 5.0.3 (Android 7.0), is here:
"/version/special_cust/BTV-W09/hw/usa/vendor/etc/cfg_btv_hisi.ini"​

As mentioned above, change the "band_5g_enable=0" to "band_5g_enable=1" with a text editor, and reboot.

*Remember* you HAVE to have root for this to work. See other write-ups in XDA-Developers website for how-to's.