You can enable a persistent connection to get alerts directly without relaying them through Google, but then you need to have a connection to your Home Assistant server all the time (eg by using a VPN or by exposing it publicly)
I don't see anything in that article that says that Google store the contents of the notification. It just says that they link push tokens to emails, which is true - they have to know who to send the push notification to.
In any case, if you don't want Home Assistant notifications being relayed through Google, you can use a persistent connection so that the app connects directly to your Home Assistant server.
Most libraries have TypeScript types these days, either bundled directly with the library (common with newer libraries), or as part of the DefinitelyTyped project.
There's a few comments like this in this thread, from people that I guess didn't actually read the post :)
They weren't asking how to do it; they were asking why it works out-of-the-box with the standard Home Assistant notifications.
You don't need ntfy; the standard Home Assistant app notifications work anywhere since they route via Google Firebase.
That's what I was thinking of! It's not in the settings section I'd expect it to be in (notifications) so I thought it wasn't doable any more.
Use TypeScript, and nonsensical things like adding arrays to objects will be compile-time errors.
Notifications go through Google Firebase servers. This is documented here: https://companion.home-assistant.io/docs/notifications/notification-details/. Your HA server sends the notification to Google, which then sends it to your phone. They don't store the notification they just relay it.
Most mobile apps do something like this. One reason is to improve battery life - your phone can have a single connection to a Google server instead of every app needing its own separate connection.
There used to be a way to use local notifications (meaning you have to be on the same network, either locally or via a VPN), but I can't find the setting any more so maybe it's gone now. (edit: this is still possible)
Vivaldi is good in some ways (I miss the old Opera and Vivaldi is a spiritual successor to it), but we really don't need more Chromium-based browsers in the world. It's becoming a Chromium monoculture, which is bad for the web.
If you want to use a different browser, try Librewolf.
Rumor has it that apps that use Real Debrid are way easier to use since you can just go to a TV show and watch it. Even a non technical person can use apps like Weyd. Real Debrid supposedly caches torrents on their server so you can instantly stream them over an encrypted connection.
I've heard that Google might have information about Real Debrid and apps that support it. I cannot confirm or deny this myself.
You can use WebAssembly today, but you still need some JS interop for a bunch of browser features (like DOM manipulation). Your core logic can be in WebAssembly though. C# has Blazor, and I wouldn't be surprised if there's some Rust WebAssembly projects. I seem to recall that there's a reimplementation of Flash player that's built in Rust and compiles to WebAssembly.