The words "multi channel" means a different code is sent for each button. It does not mean a different frequency or any other parameter. The documentation for your receiver, normally, would show you how to train the receiver to accept the code from one remote button at a time. Seems you do not have the documentation.
I don’t have any documentation of the remote controller , it came with a tubular motor , the only document is the button press order to pair the remote with the motor and adjust the turning limits of motor.
I asked the factory but they didn’t tell anything.
Using using random equipment that you dont have information for or dont know the actual low level protocols used is not a good place to start.
It might be 433Mhz but thats the same as saying its a human that is speaking, when of course they could be using a gazillion variations of languages and dialects.