default or selected kernelversion does not have config value CONFIG_COMEDI_RT.
Result is shown for kernelversion 5.14.15

Comedi Real-time support

modulename: comedi_rt.ko

configname: CONFIG_COMEDI_RT

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Comedi Real-time support
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
Enable Real time support for the Comedi core.

source code:
drivers/staging/comedi/