To add to others' advice to get your own router and use the modem only to connect to the internet (WAN), consider getting a router on which you can install OpenWRT. This will give you much more confidence that only you control your network.

I never use their device for anything other then a transceiver/bridge. I would just get my own gateway and place it inside theirs. Do get one that has updates. Replacing theirs is not a bad idea too.

Wow, never heard of anything like it though it feels plausible that your ISP would be able to do this. I'm not an expert on this in any way though, just a self-taught, self-hoster. My first thought was getting yourself another router as well, though I'm not 100% sure if this would work. I dimly remember that I had to change my ISP's router to "modem-mode" or something when I did this years back. And if your ISP doesn't allows this ...

I don't know if anyone has murmurings this yet, but if you leave a landline that is through your ISP, and connected to the router, you may not be able to use your own router. Spectrum doors not let you, and despite all the research I did before, I did not find that out until after I purchased my own. You can ask them to split the line and use the old router with the phone, and your new router for internet, but there are potential issues with degradation of service involved, as well as the more mundane problems of running into ISP support who are not interested in understanding what you want, and getting the line actually, physically split.

I have been running a TP-Link Archer C4000 for several years now. Super solid, great price, no complaints. For me the tri-band capability is more important than Wifi-AX, which isn't very useful unless you need incredibly fast network speed or if you have a ton of devices (which all need to be supporting AX).

Depending on where you live you might just let your ISP give you a modem and you can choose the router yourself. ISPs use the TR-069 protocol which allows them to manage and administrate the router they gave you. This is probably what they did when they made the changes you mentioned. It even allows them to analyze your whole home network. Thanks to this they can spy on you if they want to. So my advice is to just get a modem from them and choose your own router because then they can't spy on you. My advice is to use OPNsense, it's open source.

Edit: Bridge mode + your own router so they can't spy on your home network would also do the trick.

Btw, for the proprietary apps try Shelter/Insular and TrackerControl.

@LinkOpensChest_wav

Welcome to xFinity Xfi or whatever they call their crap.

Get your own router (that saves you 10$ a month and sparesy from this crap)

Or if you can't replace their modem, then get your own and use theirs in bridge mode

I've had bad luck with all the name brand router wifi combos. I've tried several high end models, from tplink to linksys to net gear. I've finally built a pfsense box as a router/firewall (qotom mini pc) and I've switched to ubiquity ap6 in my house. Finally something that works well for me.

Granted it depends on what you're comfortable with and what you use your devices for. I'm using vlans and vpns and different interfaces for various different things so I need the extra functionality pfsense offers.

Which ISP is doing this?

I work for a German ISP (which happens to have a big mobile phone daughter in the US) and the thought of an ISP being able to do this without anything one can do against it is bonkers to me. I was just reminded from the comments here that you folks over there usually do not have aftermarket routers with modems built in. I mean, I'm using my employers router of course since it was way cheaper than any alternative but the thing will not lock me out of any settings because if it did that, ppl would just stop using it.

I recently had a similar situation and ended up buying an Arris CM8200A modem and a TP-Link AX1500 router. I'm pretty happy with both. If you have any devices that can utilize the increased speed, I'd say the AX3000 will be worth it. You might also want a faster modem if our internet connection is faster than gigabit.