East Coast US here, I can bring my own cable modem with any cable ISP I have had in the past 10 years.

I imagine fiber is a different story.

Well, yes and no.

Providers are (I believe) required to let you bring your own equipment. Every DSL or cable service I've seen has allowed this.

However, it is also required that the modem you plug into the network accepts and runs firmware provided solely by the network operator. They can update your device at any time and there's nothing you can do about it.

So yeah, you can run your own hardware if you want, but the ISP will run their software on it whether you like it or not.

Definitely not the case. How would the firmware even end up in the device, which protocol delivers it? And which ISP would have the expertise to patch a collection of random devices in the network?

See TR-069

Thanks for the pointer, today is another day when I'm learning something new.