vjmanzo am I right to understand, that if after Y cable on a piezo out I would put something like this: https://www.lrbaggs.com/preamps-di/session-di-acoustic-guitar-preamp and then send the output of a preamp to an amp or a soundcard, I would get the sound. I did all the above mentioned but got no...

@vjmanzo thanks! but my problem seems to be worse. I split the signal into two different amps but got no signal from the piezo, no matter what position I used. That's why I thought about NiteMix as a solution, but now I think that probably something is wrong with the wiring.

Using a TRS - two mono jacks cable didn't work, I get only a magnetic signal. I'm afraid something is wrong with the guitar. Are there any diagrams on NFV-2 I can bring to a guitar tech? I searched everywhere, but can't find Thanks!

I actually bought a NiteFly NFV-2 but struggle to find a way to use a piezo tone. I searched for an analog of NiteMix External Fishman Piezo Preamp, but there are no options available.