Using this PR and instructions for dkms here:
sudo apt install -y dkms
git clone https://github.com/chasonr/rtl8822bu.git --branch linux-4.15-fix
sudo cp -r rtl8822bu /usr/src/8822bu
sudo dkms add -m 8822bu -v 1.1
sudo dkms build -m 8822bu -v 1.1
sudo dkms install -m 8822bu -v 1.1
sudo modprobe 8822bu
After this, the wifi appeared under the network settings.
Update: this no longer works after a rebootl the network connections are available but it fails to connect to any SSID. But it's a step in the right direction at least.