With all due respect, if you plugged external antenna's to the ports found outside the router, then you shouldn't be on the internal antenna. Your presumed lackluster in speed might be due to your lack of network coverage on your network operator. Might want to try and move the device close to the window or if you see a clear skied day, use it on your rooftop and see if your speeds get better.
Just as an added info, adding antenna's don't necessarily improve your speeds, if your network is crippled with too many users on it.
Is there some kind of display that will show you your signal strength. The speed may not actually increase if you already have a very strong signal.
When you have equipment that has TS9 connectors generally these are for LTE radio. There is a tiny chance they are for WIFI which is used to talk between the device and your PC. If it is wifi then you will get no better signal to the cell tower.
It depends on how they implemented the plugs. They could disconnect the internal antenna when anything is plugged in or they could just connect both sets of antenna. Just because of how radio works it will get the signal over the better antenna even with the others connected.
In any case this is not a software thing. It tends to be a physical switch in the plug if it is disconnecting the internal antenna.
I have very little actual knowledge of huawei stuff, very little equipment in the USA has these connectors because it is in the legal grey area if you can actually put antenna on a device that connects to a cell network.