I am also interested in a sniffer tool.
For the moment I am using a Dovado Tiny in bridged mode in serial with my RT-N66U. Huawei E392 or E398 as LTE/4G modem.
Tplink uses a sniffer tool
But Tplink cannot go above 22.5 Mbits and I have a 80 Mbits connection
(usual 50-60 Mbits)
EDIT Tested my Huawei E398 and it works but with the 22,5 Mbits limitation. EDIT again, also my Huawei E392 works but with the same 4G limitation.
Back to Dovado Tiny as bridge.