Latest Facebook Messenger 131 user agents:

User Agent Platform Device
Mozilla/5.0 (Linux; Android 5.0.1; LG-H340n Build/LRX21Y; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/60.0.3112.107 Mobile Safari/537.36 [FB_IAB/MESSENGER;FBAV/131.0.0.17.89;] Android 5 Leon
Mozilla/5.0 (Linux; Android 4.4.2; SCH-I435L Build/KOT49H) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/30.0.0.0 Mobile Safari/537.36 [FB_IAB/MESSENGER;FBAV/131.0.0.17.89;] Android 4 Galaxy S4 mini
Mozilla/5.0 (Linux; Android 4.4.2; CHC-U01 Build/HuaweiCHC-U01) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/30.0.0.0 Mobile Safari/537.36 [FB_IAB/MESSENGER;FBAV/131.0.0.17.89;] Android 4 G Play Mini