Did you follow the steps of the first page of this topic? Download your rom to an otg usb type-c memory and run twrp. Format data via twrp and install your rom with otg usb.
flashed the Indian version above the Chinese and network is back everything is fine except the old app closing bug on this rom https://www.nubia.com/in/support.php?a=phone&pid=27
gonna try installing Chinese rom again this sunday via twrp flash instead of stock recovery thanks after reading whole 22 pages of replies/comments from everyone kind of figured it out i.e. TWRP must be used to flash china rom+gapps..
btw anyone knows which android version is the latest chinese rom?