To disable NetworkManager and control your network configuration from command-line only, even on Ubuntu Desktop, use netplan, edit files in /etc/netplan/ and change the renderer from NetworkManager to networkd.

Wifi

Using netplan with ubuntu works for me well: when configured properly, Raspberry PI will automatically connect to wifi on boot and you can simply ssh to it.

I have the following file /etc/netplan/00-wifi.yaml:

network:
  wifis:
    wlan0:
      dhcp4: true
      optional: true
      access-points:
        "<YOUR_AP_NAME>":
          password: "<YOUR_AP_PASSWORD>"
  version: 2
  renderer: networkd

Make sure you have the netplan.io package installed. Then, run sudo netplan --debug apply and your wifi should be up - you can verify that by running ifconfig -a.

Ethernet

This is an example of a fixed-IP configuration: the machine will have the IP of 192.168.1.222 on a network with netmask 255.255.255.0, with gateway of 192.168.1.1 and two DNS servers, 8.8.8.8 and 8.8.4.4 (the Google ones):

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: no
      addresses: [192.168.1.222/24]
      nameservers:
        addresses: [8.8.8.8,8.8.4.4]
      routes:
        - to: default
          via: 192.168.1.1

Again, run sudo netplan --debug apply and verify that by running ifconfig -a.

Origin: Example with netplan fixed IP address:

Checking The Stack

To check whether the DNS work, try running host -v google.com. Verify your network stack with

$ resolvectl status

More info/fixes at Linux DNS.