default or selected kernelversion does not have config value CONFIG_RXRPC.
Result is shown for kernelversion 5.15.113

CONFIG_RXRPC (not configurable)

modulename: rxrpc.ko

configname: CONFIG_RXRPC

Linux Kernel Configuration
└─>File systems
└─>Network File Systems
└─>RXRPC
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
source code:
net/rxrpc/
depends
CONFIG_NET

is depended by
CONFIG_AFS_FS