Enabling UART2 fro Frsky @ APM2.5 Arduplane 3.4

Hello, please could someone point me on how modify the code to enable UART2? I have measured uart 2 TX with oscilloscope and there is no signal at that port at all so I think it must me disabled. Any help would be highly appreciated.

…after further research with oscilloscope I found that I can see some signal on UART2 when Telem1 protocol is set to mavlink or GPS in MP. Also there is this in code, will try to modify:
#ifndef FRSKY_TELEM_ENABLED
#if HAL_CPU_CLASS > HAL_CPU_CLASS_16

define FRSKY_TELEM_ENABLED ENABLED

#else

define FRSKY_TELEM_ENABLED DISABLED

#endif
#endif

I was unable to recompile it on windows due to g: missing, after that I tried to compile on debian with apt-get arduino libraries it compiled succesfully. After setting serial 1 to Frsky D some signal appeared and taranis found some new sensors. I have no sensors currently connected so I cannot confirm that it works but looks good for now. I hope some sensors arrive in few weeks so I will update progress later.