Settings

Android Setting

Android Settings > Notifications > {Chat Apps} (On)

LINE Setting

Settings > Notifications > Notifications (ON), Show Preview (On)

Don't forget to enable notification in each room

Messenger

Profile > Notification & Sounds > Notification previews (On)

WhatsApp

Settings > Notifications > Conversation tones (On)

KakaoTalk

Settings > Notification Settings > Message Alerts (On), Display (Sender + Message)

Telegram

Settings > Notifications and Sounds > Alert (On), Message Preview (On)