I use two LoRa capable Microcontrollers: The sender will read a Temperature sensor (DS18B20) and transmit the readings to the other. What would the simplest code look like to make this happen?
I use the Arduino Cloud with the Cloud agent for Linux. Following code works for me to test connection and OLED. In the Arduino IDE I chose "HELTEC WiFi LoRa 32 (V3)", and thats the only one that works, although I'm actually using the Wireless Stick V3.1. I won't investigate further since no problems occured. 
#include <SSD1306Wire.h>

void setup() {
  // Enable external power rail for OLED
  pinMode(Vext, OUTPUT);
  digitalWrite(Vext, LOW); // LOW = ON for Heltec
  delay(100);
  // Reset OLED
  pinMode(RST_OLED, OUTPUT);
  digitalWrite(RST_OLED, HIGH);
  delay(10);
  digitalWrite(RST_OLED, LOW);
  delay(10);
  digitalWrite(RST_OLED, HIGH);
  delay(10);

  display.init();
  display.flipScreenVertically();
display.clear();


display.drawString(0, 0, "Kibar");
display.drawString(0, 10, "Feyzo");
display.drawString(0, 20, "Merhaba!");

display.display();
}

void loop() {

}

Now lets connect a DS18B20 temperature sensor and show the readings on the oled. Pull-Up-Resistor wofür? 
#include <SSD1306Wire.h>
#include <OneWire.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS 5
#define READ_INTERVAL 2000

SSD1306Wire display(0x3C, SDA_OLED, SCL_OLED, GEOMETRY_64_32);
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

uint32_t lastRead = 0;

void setup() {
  Serial.begin(115200);

  // Power OLED
  pinMode(Vext, OUTPUT);
  digitalWrite(Vext, LOW);
  delay(100);

  // Reset OLED
  pinMode(RST_OLED, OUTPUT);
  digitalWrite(RST_OLED, HIGH); delay(10);
  digitalWrite(RST_OLED, LOW);  delay(10);
  digitalWrite(RST_OLED, HIGH); delay(10);

  display.init();
  display.flipScreenVertically();
  display.clear();
  display.drawString(0, 0, "Ready");
  display.display();

  sensors.begin();
  Serial.println("Ready");
}

void loop() {
  if (millis() - lastRead >= READ_INTERVAL) {
    lastRead = millis();

    sensors.requestTemperatures();
    float tempC = sensors.getTempCByIndex(0);

    if (tempC == DEVICE_DISCONNECTED_C) {
      Serial.println("Sensor error!");
      display.clear();
      display.drawString(0, 0, "Sensor error!");
      display.display();
      return;
    }

    Serial.printf("Temperature: %.2f C\n", tempC);

    display.clear();
    display.drawString(0, 0,  "Temperature:");
    display.drawString(0, 14, String(tempC, 1) + " \xB0C");
    display.display();
  }
}