Latest Facebook Messenger Lite 311 user agents:

User Agent Platform Device
Mozilla/5.0 (iPhone; CPU iPhone OS 14_4_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 LightSpeed [FBAN/MessengerLiteForiOS;FBAV/311.0.0.36.119;FBBV/288771643;FBDV/iPhone9,3;FBMD/iPhone;FBSN/iOS;FBSV/14.4.2;FBSS/2;FBCR/;FBID/ iOS 14 iPhone 7
Mozilla/5.0 (iPhone; CPU iPhone OS 12_5_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 LightSpeed [FBAN/MessengerLiteForiOS;FBAV/311.0.0.36.119;FBBV/288771643;FBDV/iPhone7,2;FBMD/iPhone;FBSN/iOS;FBSV/12.5.2;FBSS/2;FBCR/;FBID/ iOS 12 iPhone 6