I actually had a look. Now you can get messages and stuff from MS Graph. The situation is better than a few years ago when only very useless Teams APIs were available.

But the available APIs still suck. For example there is none to just get all recent notifications. I don't know if teams itself has access to more and better apis? If not that would explain a lot.

I wouldn't be surprised if it didn't. The number of times I've heard the notification sound, gotten a toast while in the middle of something, and then been unable to find what the hell that notification was for, because some other device I'm logged in on has helpfully marked it read.

Then begins the hunt through chats, meeting chats, group chats, channel chats and the notification pane (which doesn't show every type of notification!?) to find what it was.

Absolutely maddening.