- Power up the printer, install cartridges
- Settings -> Wi-Fi -> Setup-Wizard to connect printer to your network
- Settings -> Wi-Fi -> TCP/IP, note IP address (mine is 192.168.1.8)
- check if printer is reachable on the network: ping 192.168.1.8
- create new user "lp" in group "lp": sudo useradd -s /bin/false -g lp lp
- install driver from AUR: yay brother-dcpj4120dw