>Likewise, using privacy messengers like Signal is also useless if they can just take control of your entire device anytime they want.

Totally not useless. It costs a lot more to pay a spyware firm then to have an employee send an email / ask a judge (like that's even necessary).

I feel quite confident of my messages privacy on my Pixel with GrapheneOS given most people I message are on iPhones which are second in security to Pixels running GrapheneOS. Not to mention my threat model doesn't include mercenary spyware, as most people's doesn't.