You said that you are without internet access-
Since you don't have internet the only thing I can think of is use a friends computer and download the driver for you card to a pendrive (usb memory stick)
Or go to your local library and use their computers-
Once on the pendrive/memory stick you can cut and paste it off the memory stick and paste it to your desktop; right click and install it that way. Not sure if Black Opal has that option like my distro does. If not; you'll have to open the terminal and install using dpkg -i (name of driver)change the directory and indicate where the driver is.
Should you struggle with that you can type:
In the terminal for help.
5.8 GiB memory; you have sufficient RAM so that's a plus.
That's odd that it still comes up as Ubuntu when you have installed Black Opal-
When you installed Black Opal did you create 2 new partitions?
"08:00.0 Network controller: Realtek Semiconductor Co., Ltd. Device 8723"
This is your NIC if I'm not mistaken. The Realtek site is:
If you have trouble finding your driver let me know and I'll do what I can to help you find it-