Every device connected to the network, their Mac addresses, any unencrypted traffic. There are lots of local IoT devices that assume they’re safe behind your router. They could get info on everything you watch on TV if you have a Roku (and probably other ones too), see when you open your fridge, your thermostat
You should get your own router and access point, and put the gateway in bridge mode. Right now Comcast has direct access to your entire network
I mean, what can they see with the router that they already cant see as an ISP?
Every device connected to the network, their Mac addresses, any unencrypted traffic. There are lots of local IoT devices that assume they’re safe behind your router. They could get info on everything you watch on TV if you have a Roku (and probably other ones too), see when you open your fridge, your thermostat