In order to help protect people from falling victim to sophisticated phishing attacks, Signal introduced new user flows and in-app warnings. This work has been completed for some time and is unrelated to any current events. If you’re interested in learning more, this WIRED article from February 19th (over a month ago) goes into more detail:
https://wired.com/story/russia-signal-qr-code-phishing-attack/ 4/
WIRED · A Signal Update Fends Off a Phishing Technique Used in Russian Espionage