I don't see an issue as signal is designed not to trust the server. Signal also uses sealed sender and Perfect Forward Secrecy, which is something almost all e2ee messengers lack. What it means in practice is signal leaks very little if any metadata, if you leak metadata you give away details about who your talking to and for how long, etc. Examples might include talking with a suicide hotline, or a doctor, maybe a customer service agent at a company and for how long. Those details will give a lot away about you, even if the messages or calls themselves are encrypted. Matrix is not recommended for communication because it fails to properly hide metadata and actively trusts the servers. When you make a call on signal, as long as both users have "Always Relay Calls" set to disabled, your calls will be peer to peer instead of trusting a central server to facilitate the connection and trusting a middle man. What this means is since the connection is peer to peer you can leak your IP address to the user you're talking to, however a VPN fixes this issue.
As far as it being against signals tos, molly exists and had not received any problems from the signal foundation to my knowledge, discord has the same clause and they don't seem to give a rats ass. Sure they could enforce it but they don't, and personally with how matrix clients are handled they have mixed security, fluffychat has security issues ranging from outdated SDK versions to quite literally ddosing homeservers because of a non-existent rate limit.
The crypto stuff wasn't great but you know what's cool? You don't have to use it. Simple as that. You don't have to engage with it and you and I both know that. It's buried in settings and you have to find it yourself.
Signal is not an anonymity tool, and has never been advertised as such, if you need anonymity, signal is not a good choice. You can make it more anonymous by using a burner phone but that's a different topic.
If everything is encrypted, what could Amazon tap? You do realize sealed sender and PFS take away any trust from the server correct? It's all encrypted, your aren't trusting the server at all, it's completely trust-less, and unless you think Amazon or governments can at this very moment tap any encrypted data and decrypt it, I would recommend taking a walk outside and realize that no one, NO ONE can decrypt current encrypted standards.
Unless you can point me to a reputable article showing in great detail that signal is lying about their e2ee claims then I'll rest my case. Signal has been proven time and time again to not have any data on their users except the minimum required for the service to work, that's called integrity.
Also there will always be someone you trust on the internet, nothing will change that unless we completely rethink how the internet works.
Edit: added quotes Edit 2: added extra info