Latest Facebook Messenger 98 user agents:

User Agent Platform Device
Mozilla/5.0 (Linux; U; Android 4.3; es-us; SM-G350M Build/JLS36C) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30 [FB_IAB/MESSENGER;FBAV/98.0.0.18.71;] Android 4 Galaxy Core Plus
Mozilla/5.0 (Linux; U; Android 4.0.4; es-us; GT-S5301L Build/IMM76D) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30 [FB_IAB/MESSENGER;FBAV/98.0.0.18.71;] Android 4 Galaxy POCKET Plus
Mozilla/5.0 (Linux; Android 6.0.1; SM-J500FN Build/MMB29M; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/49.0.2623.105 Mobile Safari/537.36 [FB_IAB/MESSENGER;FBAV/98.0.0.18.71;] Android 6 Galaxy J5 (2015)
Mozilla/5.0 (Linux; Android 5.1; M3s Build/LMY47I) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/40.0.2214.117 Mobile Safari/537.36 [FB_IAB/MESSENGER;FBAV/98.0.0.18.71;] Android 5 M3s
Mozilla/5.0 (Linux; Android 5.1.1; Nexus 10 Build/LMY49J; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/54.0.2840.85 Safari/537.36 [FB_IAB/MESSENGER;FBAV/98.0.0.18.71;] Android 5 Nexus 10
Mozilla/5.0 (Linux; Android 5.1.1; KIW-L21 Build/HONORKIW-L21; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/54.0.2840.85 Mobile Safari/537.36 [FB_IAB/MESSENGER;FBAV/98.0.0.18.71;] Android 5 Honor 5X
Mozilla/5.0 (iPad; CPU OS 8_1 like Mac OS X) AppleWebKit/600.1.4 (KHTML, like Gecko) Mobile/12B410 [FBAN/MessengerForiOS;FBAV/98.0.0.25.70;FBBV/44186053;FBRV/0;FBDV/iPad4,4;FBMD/iPad;FBSN/iPhone OS;FBSV/8.1;FBSS/2;FBCR/;FBID/tablet;FBLC/en_GB;FBOP/5] iOS 8 iPad Mini 2