Technically this is present on the Remarkable if you're willing to fiddle with the device some. They give you root by default (and provide an ssh service if the device is connected over usb), and the community has implemented quite a few syncing options.
That said - I was also very bummed to see them introduce the paid service. I'd really like them to succeed by selling good & open hardware, not by moving towards a locked down device ties to SaaS.
Clarification: the above are apps for which I still want /useful/ notifications, so I can't disable all notifications for them out-right.
I also feel like you for the paid Connect account, which I work around using open source tools that you're free to run on it. You can SSH as root easily and run whatever you want. I do it frequently for screen sharing.
I for one find the lack of progress astonishing. Because, you know, if you wanted great writing experience you could've used a CrossPad ... 25 years ago. You write on a notebook -- with a quality pen manufactured by Cross as the name suggests -- the CrossPad records it as vector strokes. Done. In 25 years the progress we got is there's a screen now but that's all. The device still can't do, say, offline OCR or indeed anything useful beyond what the CrossPad used to do.
I've had other devices with pens, but never really used them. I got the Remarkable for my wife and it really compels me to use it, but not with any features, just the writing aspect. I can't tell you whether it's the texture, the screen or something else, but it just does. I admit the same could happen with other E Ink writing devices like the Onyx Max Lumi 2, but I don't have any of them to confirm.
Like syncing local notes using common cloud services?
Technically, the feature's there, but it's locked behind a $100 per year "service".
Rant aside, I have an iPad mini where I turned all notifications off. Just as good as if it didn't have those features when I don't care about them - but if I need them they're right there.