My wifi mysteriously died in Ubuntu 18.04 for my dual-boot desktop, again. Just a quick heads-up, my desktop does not have a built-in wifi adapter. I purchased a USB dongle a couple years ago, namely the D-link DWA-182 version C to enable it to connect to wifi. It died because linux kernel has been updated from Ubuntu 16.04 to 18.04, and my old driver no longer builds properly.
Here’s what I did to fix it:
git clone https://github.com/gnab/rtl8812au
This particular version: https://github.com/gnab/rtl8812au is updated to compile against kernel 5.2.
After getting the code, navigate to the repository, then run:
sudo make
sudo cp 8812au.ko /lib/modules/$(uname -r)/kernel/drivers/net/wireless
sudo depmod -a
Blog for Open Source Software 