Trying to build LIN_master_portable/examples/LIN_HardwareSerial_ESP32_Background/LIN_HardwareSerial_ESP32_Background.ino fails with:

In file included from /home/dave/Arduino/libraries/LIN_master_portable/src/LIN_master_SoftwareSerial.cpp:14:
/home/dave/Arduino/libraries/LIN_master_portable/src/LIN_master_SoftwareSerial.h:25:10: fatal error: SoftwareSerial.h: No such file or directory
 #include <SoftwareSerial.h>
          ^~~~~~~~~~~~~~~~~~
compilation terminated.

This is with esp32-arduino 2.0.9 release. I've checked back to the 2.0.0 and 1.0.6 releases and it doesn't appear to work there either. From what I can see SoftwareSerial is not supported by the ESP32 Arduino core due to issues with reliable bit timing due to the FreeRTOS base.

The build problem is possible to work around by removing || defined(ARDUINO_ARCH_ESP32) from the list of supported platforms in the top of LIN_master_portable/src/LIN_master_SoftwareSerial.cpp.