Well since the rom as root, just edit system build.prop or is vendor build.prop… well in one of the two LOL i just cant be sure now, just check both build.prop…
And just comment out ( put a # in the beginning ) ro.boot.wificountrycode=CN , save and reboot and voila 5g back.
In the sdk just go to kvim3.mk, kvim3l.mk and comment ( put a # in the beginning ) the :
PRODUCT_PROPERTY_OVERRIDES +=
ro.boot.wificountrycode=CN
And that is it!