Why does "LoRa.begin" fail here?

yes - read thru post 6
what do you wish to do? we may then be able to recommend a suitable lora module and host microcontroller, e.g. have a look at TTGO LoRa32 SX1276 OLED - it supports lora peer-to-peer using lora.h library and LoRaWAN using the TTN_esp32.h library