Google "grapheneos arguments controversy" "grapheneos rossmann" etc for a history of that project to decide if you really want that software on your device.
For more info on the project, there is a post on 'Chinese gooseberry' Farms with a lot information - not that I endorse any of the Doxxing/Swatting etc in that community behaviour - it purely serves as an archive of many deleted social media posts etc.
The most secure device is no device. I don't recommend any mobile OS. I don't recommend GrapheneOS. I don't recommend Android. I don't recommend iOS.
Nothing in this is libel in any jurisdiction. The above is my personal opinion.