Quick update here. I received the XSR receiver today,
https://hobbyking.com/en_us/frsky-xsr-2-4-ghz-accst-receiver.html?___store=en_us and I bound it with the multiprotocol module. Just some important things to keep in mind:
First, it comes with no connector, so you have to provide one. I salvaged a futaba like connector from a dead servo.
Then you have to solder the wires. Black to black (GND), red to red (+), the yellow is for telemetry, so I did not touch it (yet, lol), the green is for CPPM, which I left untouched too, and the white is the SBUS one, and you have to connect it too.)
Then for binding the module, is important to choose the Protocol, which is FrskyX, the type (that means, the firmware the receiver has, EU16ch (Europe) or CH16 (China) it was china in my case. You can change the software in the receiver, but why to bother if you can select the one you have with the radio?
After some unsuccesfull tries binding, I found in a forum that I had to change the module frecuency. The stock frecuency is set to 0 and the tutorial said to first try with +40 or -40. If it does not work, to keep increasing the numbers until it works. In my case it worked with +40.
Then I connected the Open Panzer board to the computer, and in the "Op config" program I clicked on "read radio" and then I was able to check that my receiver was receiving all my signals.
I am very happy now and this is only the beginning!
EDIT: This is my first receiver with telemetry. Do you have any idea of what do I need or what do I have to do to see the battery voltage in my radio?