https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode

Once you’ve enabled bridge mode, you can follow the directions that came with your router to set it up, and it’ll auto detect everything. You can do DNS in your router.

I can’t recommend ubiquity enough:

https://store.ui.com/us/en/collections/unifi-dream-router

Even a router from Walmart should do DNS, just avoid the Google ones if you want control. They work good, but very few options. I’ve heard TPLink is good.