I keep seeing references to this from Americans, but is this actually a thing? There’s no way my ISP would allow me to connect a device that isn’t owned by them.
The cable company resisted it but ultimately published a how-to as well.
https://www.ziggo.nl/klantenservice/apparaten/wifi-modems/ei...
Further, my experience with Comcast specifically is that every three months, they "forget" that I don't rent a modem from them and just start charging me the rental fee anyway. Then I have to call them up to tell them to remove the charges and stop adding new ones.
But for the record:
If you just sign up for Comcast (XFinity, whatever) and use the internet, you are renting a modem/router combo from them for about $10 a month, in perpetuity. You can buy an off the shelf modem/router for a couple hundred bucks, and use that instead. It'll pay off in a year or two. You have to call Comcast up and activate the device, but it's otherwise a completely painless process.
Not only can you do it in the US, but the cable company will give you clear instructions on how to get it set up and running on their system.
And it's a good idea. Not only to avoid paying the modem rental fee, but also because the modem provided by cable companies tends to be pretty awful.