Latest Facebook Messenger Lite 256 user agents:

User Agent Platform Device
Mozilla/5.0 (iPhone; CPU iPhone OS 13_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML like Gecko) Mobile/15E148 LightSpeed [FBAN/MessengerLiteForiOS;FBAV/256.0.1.26.113;FBBV/203261359;FBDV/iPhone10 1; iOS 13 iPhone
Mozilla/5.0 (iPad; CPU OS 13_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 LightSpeed [FBAN/MessengerLiteForiOS;FBAV/256.0.1.26.113;FBBV/203261359;FBDV/iPad5,4;FBMD/iPad;FB iPadOS 13 iPad Air 2