"Lock Screen Protection" is the second line of defense for your local privacy in the app. Go to Security Center > Lock Screen Protection.
Settings
Create lock-screen password: enter the lock-screen password twice to set it.
Lock Screen Protection (toggle): when on, the app auto-locks while running in the background and can be unlocked with the lock-screen password.
Lock-screen password (once set, can be changed).
Lock timing: every time, 1 min, 5 mins, 30 mins.
Face ID (toggle): once on, you can unlock with the system Face ID.
Destruction password (toggle): unlocking with it permanently deletes all chat records — irreversible.