Your inputs don’t match the mixer at present. The channel order is different. It should be AETR on both from channels 1-4. 1- Aileron, 2- Elevator, 3- THROTTLE, 4- Rudder. Move the Throttle in inputs to the right place.
You should also set up your aux channels in there. Have a look at this video , the screens are slightly different but Jumper uses a slight change to OpenTX, the basic workflow is the same.
You should also set all your endpoints up so the bottom of the sticks is 1000 and the top is 2000. Calibrate the gimbals through the radio first.
If having everything above set up doesn’t get you armed then you need to change the minimum throttle value, use the CLI command
Look at the value. If it’s lower than the bottom value of your throttle stick then it won’t arm. Read your min throttle value, then use
set min_check XXXX
The four XXXX would be swapped for your minimum throttle value plus 10.
Sorry, I see what you mean about the Channel inputs. I may have only changed one of them to make it work on the BetaFlight and may have forgot to change it in the inputs.