How would they scan Signal messages? Via iPhone and Google Android backdoors? That's the only way I can think of. Always use a custom ROM like GrapheneOS.
Discussion
Doesn't need a backdoor Apple Intelligence and Google Gemini can see what your doing
And unencrypted backups
On Appe and Google phones, or GrapheneOS? Surely you'd need to drop the ball somehow and let their malware in.
On iOS or PixelOS where AI is built in to the operating system.