nmtui

Old advice for setting a Raspberry Pi IP address to a static IP on the Pi itself said to edit the /etc/dhcpcd.conf file, and add it there.

But on Raspberry Pi OS 12 and later, dhcpcd is no longer used, everything goes through Network Manager, which is configured via nmcli or nmtui. If you're booting into the Pi OS desktop environment, editing the IP settings there is pretty easy.

But setting a static IP via the command line is a little different.

First, get the interface information—you can get a list of all interfaces with nmcli device status:

$ nmcli device status
DEVICE         TYPE      STATE                   CONNECTION         
eth0           ethernet  connected               Wired connection 1 
lo             loopback  connected (externally)  lo                 
wlan0          wifi      disconnected            --                 

In my case, I want to set an IP on eth0, the built-in Ethernet.