But, signal has the concept of sealed sender (https://signal.org/blog/sealed-sender/), where signal doesn’t know who is sending the messages.

This is when the government asked for data from Signal, “The only Signal user data we have, and the only data the US government obtained as a result, was the date of account creation and the date of last use – not user messages, groups, contacts, profile information, or anything else.” (https://signal.org/blog/looking-back-as-the-world-moves-forward/)

With my phone number, they could tie it to other services, but not with the contacts in Signal itself.

This is something related to how groups are secured - https://signal.org/blog/signal-private-group-system/

But, we could install a version of signal client that’s not compromised, which sends as little as possible, encrypted. So, a compromised server could deny the requests, because the client was modified or it couldn’t work with the encrypted content the way it expected. This would automatically raise red flags, because the app doesn’t work anymore. Has something like this happened?

And for the deploying modified versions to targeted devices. I know it’s possible through orders or compromised server, but has it happened? If so, any sources regarding that.