I've not seen anything, in fact the Cert pinning is damn solid! We have to disable Zscaler SSL inspection to even allow Signal (npub1rkw…5q62) to work.
The only issue I saw with Signal possibly "compromised" in any way was when Twilio was compromised as they did use them for verification services.
But that was like two years ago and since then they've also added usernames so you don't need to give out phone numbers
https://support.signal.org/hc/en-us/articles/4850133017242-Twilio-Incident-What-Signal-Users-Need-to-Know