Latest Amazon Fire HDX 8.9 user agents:

User Agent	Browser	Platform
Mozilla/5.0 (Linux; Android 5.1.1; KFSAWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/108.18.4 like Chrome/108.0.5359.220 Safari/537.36	Mobile Silk 108	Fire OS 5
Mozilla/5.0 (Linux; Android 5.1.1; KFSAWI Build/LVY48F; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/59.0.3071.125 Safari/537.36[FBAN/EMA;FBLC/en_US;FBAV/448.0.0.11.101;FBCX/modulariab;]	Facebook Lite 448	Fire OS 5
Mozilla/5.0 (Linux; Android 4.4.3; KFSAWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/44.1.81 like Chrome/44.0.2403.128 Safari/537.36	Mobile Silk 44	Fire OS 4
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFSAWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.68 like Chrome/39.0.2171.93 Safari/537.36	Mobile Silk 3	Fire OS 4
Mozilla/5.0 (Linux; Android 5.1.1; KFSAWI Build/LVY48F; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/59.0.3071.125 Safari/537.36 [Pinterest/Android]	Pinterest	Fire OS 5