default or selected kernelversion does not have config value CONFIG_LIRC_SERIAL_TRANSMITTER.
Result is shown for kernelversion 6.5.1
Serial Port Transmitter
configname: CONFIG_LIRC_SERIAL_TRANSMITTER
Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Media staging drivers
└─>Linux Infrared Remote Control IR receiver/transmitter drivers
└─>Serial Port Transmitter
In linux kernel since version 2.6.36 (release Date: 2010-10-20)
Serial Port Transmitter support