Permanently change IP address on Ubuntu Server 21.10

# Install net-tools (if not already)
sudo apt-get install net-tools

# Get your netmask...
ifconfig
# Look for the bit with the label of 'netmask'. In my case it's 'netmask 255.255.255.0'

# Assuming your interface is called eth0, change the IP by issuing...
sudo ifconfig eth0 192.168.1.234 netmask 255.255.255.0