Wifi on Ubuntu 18 server

TLDR

1. Install wpasupplicant
2. Turn on wifi radios: sudo nmcli radio wifi on
3. Check your devices are recognised even if they're not "managed": sudo iwconfig
4. Check your wifi (here called "wlp3s0") is capable of detecting nearby routers: sudo iwlist wlp3s0 scan
5. Configure netplan by dropping a file called 01-netcfg.yaml into /etc/netplan/ or edit existing file there. See example below.
6. netplan try, netplan generate, netplan apply.