It runs some flavour of Linux.
In the past I’ve maintained a custom FreeBSD or Linux server for this purpose but life’s too short.
Just ordered a UniFi AP for home, we use them at work and they have been very good. I have ordered a seperate VDSL modem too (Openreach from ebay until I save for a Draytech 130).
I really like the look of the Unifi router...maybe next pay day!
In front of the Linux there was a cable-modem, and behind there where a couple DMZs, with servers, and wifi, and my home LAN.
I had my own DNS/DHCP servers.
Almost all services were internal (files, webs, git, streaming, databases, backups, monitoring...)
Nowadays, my home is rented, and i live in a nomad way were i get job. Just one laptop.
Their product is really simple to set up, offers a simplified “work for most” default setup but it also lets you dig into the router config details of you care.
It also offers a separate ssid for guests that only tunnels to internet and does not allow device to device communication on the lan.
There is something to be said for not requiring a lot of active effort.
FYI I don’t host or run any internet facing services from my home network.
Easy to set up, performs incredible compared to the garbage netgear router it replaced, and I have at least some confidence that the firmware will be regularly updated, or updated to patch security vulnerabilities, which I can't say about anything from linksys/netgear/etc...
Pfsense obviously would allow updates, but again, convenience...
Google has essentially bugged the whole Internet so it doesn't matter if your first hop is via a Google WiFi router that looks at each and every packet that leaves your house.