I am in the process of switching to graphene from iOS, which is slightly painful but I am sure will be worth it.
One thing which surprised me is that it seems there is no option for extra security on the SMS app.
This is important because although SMS is not habitually used in modern life, various ancient services still serve TOTP/password reset tokens via SMS, or have that as an option (I do not even know which ones!). In the event that your phone is snatched in an unlocked state, the thief would have access to SMS and therefore these tokens for some services.
iOS, for all its faults, does have the option of securing all apps with biometrics/passcodes at the os level which is useful in this regard. Android relied on per app arrangements, and there is not one for the default sms app.
Can anyone suggest a solution to this problem please?