Latest Fire OS 7 user agents:

User Agent Browser Device
Mozilla/5.0 (Linux; Android 9; KFKAWI Build/PS7331.4463N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/138.0.7204.244 Safari/537.36 [FB_IAB/FB4A;FBAV/551.1.0.58.63;IABMV/1;] Facebook 551 Fire HD 8 (2018)
Mozilla/5.0 (Linux; Android 9; KFTRPWI Build/PS7331.4463N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/138.0.7204.244 Safari/537.36 [FB_IAB/FB4A;FBAV/551.1.0.58.63;IABMV/1;] Facebook 551 Fire HD 10 Plus (2021)
Mozilla/5.0 (Linux; Android 9; AFTALMO Build/PS7708.5501N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/138.0.7204.168 Mobile Safari/537.36 Chrome Webview 138 Unknown
Mozilla/5.0 (Linux; Android 9; KFMAWI Build/PS7331.4463N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/138.0.7204.244 Safari/537.36 [FB_IAB/FB4A;FBAV/551.1.0.58.63;IABMV/1;] Facebook 551 Fire HD 10 (2019)
Mozilla/5.0 (Linux; Android 9; KFMAWI Build/PS7331.4463N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/138.0.7204.244 Safari/537.36 [FB_IAB/FB4A;FBAV/549.0.0.61.62;IABMV/1;] Facebook 549 Fire HD 10 (2019)
Mozilla/5.0 (Linux; U; Android 9; KFTRWI Build/PS7323.2834N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/100.0.4896.127 Safari/537.36 OPR/63.0.2254.61942 Opera 63 Fire HD 10 (2021)
Mozilla/5.0 (Linux; U; Android 9; KFONWI Build/PS7329.3851N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/124.0.6367.248 Safari/537.36 OPR/19.0.2254.108926 Opera 19 Fire HD 8 (2020)
Mozilla/5.0 (Linux; U; Android 9; KFONWI Build/PS7327.3329N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/112.0.5615.197 Safari/537.36 OPR/72.0.2254.67128 Opera 72 Fire HD 8 (2020)
Mozilla/5.0 (Linux; U; Android 9; KFONWI Build/PS7327.3329N; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/112.0.5615.197 Safari/537.36 OPR/59.0.2254.59153 Opera 59 Fire HD 8 (2020)
Mozilla/5.0 (Linux; U; Android 9; KFMAWI Build/PS7310; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/70.0.3538.110 Safari/537.36 OPR/40.1.2254.138129 Opera 40 Fire HD 10 (2019)
Mozilla/5.0 (Linux; U; Android 9; KFKAWI Build/PS7317; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/84.0.4147.125 Safari/537.36 OPR/94.0.2254.78762 Opera 94 Fire HD 8 (2018)
Mozilla/5.0 (Linux; U; Android 9; es-es; KFONWI Build/PS7331.4463N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.7204.224 Mobile Safari/537.36 PHX/19.5 Phoenix Browser 19 Fire HD 8 (2020)
Mozilla/5.0 (Linux; Android 9; KFTRWI; Flow) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/367.0.0.299 Safari/537.36 Flow Browser Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.7.2 like Chrome/98.0.4758.136 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.6.10 like Chrome/98.0.4758.136 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.5.8 like Chrome/98.0.4758.136 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.4.4 like Chrome/98.0.4758.136 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.4.4 like Chrome/101.0.4896.126 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.4.4 like Chrome/100.0.4871.99 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)
Mozilla/5.0 (Linux; Android 9; KFTRWI) AppleWebKit/537.36 (KHTML, like Gecko) Silk/98.2.4 like Chrome/98.0.4758.123 Safari/537.36 Mobile Silk 98 Fire HD 10 (2021)