Signal takes steps to reduce the amount of metadata visible, like sealed sender which makes it so that Signal doesn't know who sent a message. Even your payment information for donations is separated from your identity so that they know you are a donor, but not how you donated.
It desn't matter if Signal were hosted on Putin's personal servers. Its security is in its protocol, it's not trust based.
Thanks for the reply but please check the article:
Sealed Sender is Flawed
Signal has a flawed system called “Sealed Sender”, which encrypts the metadata of who sent the message inside the encrypted packets. However, cybersecurity researchers from the University of Colorado Boulder, Boston University, George Washington University, and U.S. Naval Academy, found that Sealed Sender could be compromised by a malicious cloud host in as few as 5 messages to reveal who is communicating with who. In this paper published by NDSS, headed by Ian Martiny, these researchers found that Signal’s “read receipts”, which lets the sender know that the receiver got the message can be used as an attack vector to analyze traffic because it sends data packets right back to the sender. Therefore, our recommendation to increase metadata protection is turn off read receipts, which can be toggled in the security settings.
Source used:
Improving Signal’s Sealed Sender
Ian Martiny∗, Gabriel Kaptchuk†, Adam Aviv‡, Dan Roche§, Eric Wustrow∗
∗, {ian.martiny, ewust}@colorado.edu
†Boston University, kaptchuk@bu.edu
‡George Washington University, aaviv@gwu.edu
§U.S. Naval Avademy, roche@usna.edu
Signal doesn't promise anonymity. If you're using Signal with the intent of being anonymous, well, there are better services for that. For sending E2EE messages, Signal does well; that is its purpose.