# install it
sudo apt install squid

# back up config
sudo cp /etc/squid/squid.conf /etc/squid/squid.conf.original


sudo nano /etc/squid/squid.conf
# edit stuff per https://ubuntu.com/server/docs/proxy-servers-squid
# or leave default port 3128

Example config:

acl SSL_ports port 443
acl Safe_ports port 80          # http
acl Safe_ports port 21          # ftp
acl Safe_ports port 443         # https
acl Safe_ports port 70          # gopher
acl Safe_ports port 210         # wais
acl Safe_ports port 1025-65535  # unregistered ports
acl Safe_ports port 280         # http-mgmt
acl Safe_ports port 488         # gss-http
acl Safe_ports port 591         # filemaker
acl Safe_ports port 777         # multiling http
acl CONNECT method CONNECT

# ALAN
acl mynetwork src 10.1.10.0/24

# ALAN
http_access allow mynetwork

# Deny requests to certain unsafe ports
http_access deny !Safe_ports

# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports

# Only allow cachemgr access from localhost
http_access allow localhost manager
http_access deny manager
http_access allow localhost
http_access deny all

http_port 3128

coredump_dir /var/spool/squid

refresh_pattern ^ftp:           1440    20%     10080
refresh_pattern ^gopher:        1440    0%      1440
refresh_pattern -i (/cgi-bin/|\?) 0     0%      0
refresh_pattern (Release|Packages(.gz)*)$      0       20%     2880
refresh_pattern .               0       20%     4320

Then:

#restart service
sudo systemctl restart squid.service

# watch the logs
sudo tail -F /var/log/squid/*.log