To complete our router, we need a DHCP server and DNS server. The DHCP server will assign IPs to our internal network, while the DNS server will resolve our queries to their corresponding IPs.
A while back, I started using a Raspberry Pi 4B with 2GB of RAM as my home router.
The reason for doing this is because my ISP modem is pretty basic and limited. I also didn't want to have to reconfigure my network each time I changed modem or ISP.