What about a Windows update that “mistakenly” uninstall Windows itself?

Unfortunately all other solutions are either less private (like using a browser that supports FCM only for outlook), or need a self-hosted server (like using Gotify Android app)

I’m not sure but isn’t there a notification permission for the site on browser?

IIRC leak already happened and hackers already have the data now

What about using web version? Are there any limitations compared to the app?