Oppo
Turn Lock Screen Notifications On or Off auf Oppo
On Oppo phones running ColorOS, lock screen notifications are controlled separately from the main notification shade. Each app has its own toggle, which explains why some apps still show full previews while others stay hidden even though notifications are generally allowed.
The setting sits inside the notification management area rather than the lock screen settings, which is why many users look in the wrong place first. Go to Tap on Settings ➔ Tap on Notifications & status bar ➔ Tap on Manage notifications ➔ Tap on Lock screen notifications, then pick the app you want to adjust.
From there you choose between Display title and body, Display title only or Do not show. The first option shows the full message content, the second hides the content but keeps the sender name visible, and the third removes any trace of the notification from the lock screen.
This is the setting to use if you share your phone occasionally or just do not want message content visible without unlocking. If you want to stop notifications entirely, including sound and the status bar icon, disable the app in the general notification list instead of just the lock screen option.