Fixed IP Address in Raspberry PI OS
Raspberry PI OS uses dhcpcd to configure IP, edit /etc/dhcpcd.conf as below for fixed IP.
interface eth0
static ip_address=192.168.1.16/24
static ip6_address=fd51:42f8:caae:d92e::ff/64
static routers=192.168.1.254
static domain_name_servers=192.168.1.255