Some example code I wrote for /u/reebs12 on Reddit - https://www.reddit.com/r/gamedev/comments/99y7bb/_/e4raz6j/

Reebs12Example.cpp

#include <Irrlicht.h>
#include <iostream>

using namespace irr;
using namespace irr::core;
using namespace irr::scene;
using namespace irr::video;
using namespace std;

int main()
{
    // Create device
    IrrlichtDevice* device = createDevice(EDT_OPENGL);

    if (device == nullptr)
    {
        cerr << "Could not initialize graphics device." << endl;
        return 1;
    }

    device->setWindowCaption(L"Plane rendering demo for /u/reebs12");

    IVideoDriver* video = device->getVideoDriver();
    ISceneManager* sceneManager = device->getSceneManager();

    // Add camera to scene
    ICameraSceneNode* camera = sceneManager->addCameraSceneNode(nullptr, vector3df(0.f, 0.f, -10.f), vector3df(0.f, 0.f, 0.f));

    // Create the plane mesh
    SMesh* plane = new SMesh();
    SMeshBuffer* planeMeshBuffer = new SMeshBuffer();

    planeMeshBuffer->Vertices.push_back(S3DVertex(/* position */ 1.f, 1.f, 0.f, /* normal */ 0.f, 0.f, 1.f, /* color */ SColor(255, 255, 0, 0), /* uv */ 1.f, 1.f));
    planeMeshBuffer->Vertices.push_back(S3DVertex(/* position */ 0.f, 1.f, 0.f, /* normal */ 0.f, 0.f, 1.f, /* color */ SColor(255, 255, 0, 0), /* uv */ 0.f, 1.f));
    planeMeshBuffer->Vertices.push_back(S3DVertex(/* position */ 1.f, 0.f, 0.f, /* normal */ 0.f, 0.f, 1.f, /* color */ SColor(255, 255, 0, 0), /* uv */ 1.f, 0.f));
    planeMeshBuffer->Vertices.push_back(S3DVertex(/* position */ 0.f, 0.f, 0.f, /* normal */ 0.f, 0.f, 1.f, /* color */ SColor(255, 255, 0, 0), /* uv */ 0.f, 0.f));

    planeMeshBuffer->Indices.push_back(3);
    planeMeshBuffer->Indices.push_back(1);
    planeMeshBuffer->Indices.push_back(0);

    planeMeshBuffer->Indices.push_back(3);
    planeMeshBuffer->Indices.push_back(0);
    planeMeshBuffer->Indices.push_back(2);

    plane->recalculateBoundingBox();
    plane->addMeshBuffer(planeMeshBuffer);

    // Add the plane mesh node
    IMeshSceneNode* planeNode = sceneManager->addMeshSceneNode(plane);
    planeNode->setMaterialFlag(EMF_LIGHTING, false); // There's no lights in this scene, so disable lighting.

    // Don't need the mesh anymore, so we can drop the references to it
    plane->drop();
    planeMeshBuffer->drop();
    plane = nullptr;
    planeMeshBuffer = nullptr;

    // Hint: Adding an animator would've revealed that your plane was just invisible from the angle you were looking
#if false
    ISceneNodeAnimator* animator = sceneManager->createRotationAnimator(vector3df(1.f, 0.f, 1.f));
    planeNode->addAnimator(animator);

    animator->drop();
    animator = nullptr;
#endif

    // Render the scene
    while (device->run())
    {
        video->beginScene(true, true, SColor(255, 255, 0, 255));
        sceneManager->drawAll();
        video->endScene();
    }

    // Cleanup
    device->drop();
    return 0;
}