This is a very very odd and confusing situation:
What do we do:
We check if we are connected to the internet by checking wifi and mobile connection state on the phone (This should be enough as offline persistence is enabled anyway for our project and we just want to display a hint to the user)
What is the problem
Now it gets VERY suspicious. One of the internet providers in Germany send routers to the users that are UNABLE to connect to espacially firebase/firestore servers. This happend to at least 3 different persons that own that special router. The provider told me there is no port blocking and no other restriction. There are just routers that won't connect for whatever reason. This also means that internet works but the data will never gets synchronized while the user uses wifi.
Also the enduser cannot access any portblocking/portforwarding feature. All manages by the provider. I had to request a new router 4 times until I got one that allowed access to the server. And now when I test the app at a friends place - same issue. No connection until wifi is disabled - Same provider, same router and the provider of course says there is no known issue.
The question
Is there a way to check if the connection to firebase is established (Maybe pinging the IP of firestore? Which one is it?) Or is there maybe a method providing exactly that kind of information