With no official opt-out from Recall, Signal says it was forced to devise its own method to block screenshots. The new feature is now on by default.

Windows Recall includes settings to control which apps can be captured, and it’s also possible to delete snapshots, but the makers of Signal felt the need to add a security laye

Microsoft's Recall is like a time machine that lets you explore your usage history by taking snapshots every few seconds. It's risky, but it changed how I work.