desperatemouselives Just hope GOS works well against most already known threats
GrapheneOS patches the OS and firmware very quickly as soon as updates are made available by Google. Security updates protect us from the known threats. You can read this part of the website for some more info about how GrapheneOS always patches quickly and is in other ways way ahead of other OSes.
The other, and I'd argue, bigger issue is the unknown threats. Here's a relevant page from the website about protecting against unknown threats.
It's my understanding that malicious actors usually use social engineering to trick people into actually installing malicious software. It's also my understanding that zero-click exploits generally send payloads that can exploit some sort of memory defect. GrapheneOS's hardened_malloc
helps protect against the most common classes of memory defects. So finding exploits that work on GrapheneOS is much harder than on the Stock OS.
Finally, it's important to consider the likelihood of being targeted by a sophisticated attack. Reportedly, exploits can go for millions of dollars on the black market. These kinds of exploits are not just used on tons of people (which would make the exploit easier to detect), but instead would be used to target high-profile and influential people. Any exploit that makes it out into the public and is spread out everywhere would be one that does basically nothing, like one that makes an app crash and nothing else. A nuisance, sure, but not one that puts your personal data at risk.