App badge counts and notifications have suddenly "broken"

Absolutely nothing has changed on my phone since the cause of this. I'm on an iPhone SE (2022). This has happened since the stable iOS update prior to 17.6 and has persisted after that update. The only thing I can pinpoint happened at roughly the same time was that my phone was given the option to update to iOS 17.6 at this same time.

Out of nowhere, all non-iOS notifications no longer work on my phone. Notifications from Weather and Wallet work perfectly fine, for example, but every third-party app is not sending push notifications. These same apps are also not having their badges updated (i.e., new unread emails on Gmail) until the app is actually accessed.

It's almost as if Background App Refresh has totally stopped working for every third-party app, but this is not the case.

And yes, I've tried all of the obvious:

1. My phone is not on DND.
2. Notifications are enabled for every app.
3. No Focus mode is enabled.
4. Background App Refresh is on.

To give a real example: When receiving a Discord DM, I would previously receive a banner notification, as well as an app badge increment. Neither of those things now occur upon receiving a Discord DM. When I now open the Discord app, after several seconds, it "updates" and shows new messages. All applications are behaving as if they are not being able to poll for updates or new data in this way.

This is pretty ridiculous to happen, completely out of nowhere. I've seen similar threads where people are suggesting to reinstall every application (which I've tried, starting with one app, which achieved nothing) and reset your phone. These are not solutions. This is Apple creating hours and hours of work for its users, and in some cases data is irrecoverable (such as Wallet information). I don't want to risk wiping my phone, which would take many hours to fully restore, at the off chance that it might fix the issue, despite seeing many others say it hasn't.

This has been posted about dozens of times. Why has Apple refused to acknowledge it? This is beginning to make me believe it's a case of forced obsolence—something Apple is doing deliberately in order to inconvenience users just enough so that they are nudged towards just purchasing a new phone.

We would appreciate answers. Assuming this continues to go unaddressed, this will be the final straw for me before switching to Android.