This example uses OpenLayers v10.9.0. The latest is v.
Edit

#### SVG Layer

svg 2 layer 4 render 4 transform 1

#####

Example of a map with an interactive svg layer.

With a plain `ol/Layer` and a `render` function, we can use an interactive svg as layer. Hover over countries to see the interactivity that is defined purely with a css `:hover` pseudo-class. Other layers can be added to the same map. The blue circle is a vector feature on a separate layer.

##### main.js

    import Feature from 'ol/Feature.js';
    import Map from 'ol/Map.js';
    import View from 'ol/View.js';
    import Point from 'ol/geom/Point.js';
    import Layer from 'ol/layer/Layer.js';
    import Vector from 'ol/layer/Vector.js';
    import VectorSource from 'ol/source/Vector.js';
    import {composeCssTransform} from 'ol/transform.js';

    const map = new Map({
      target: 'map',
      view: new View({
        center: [0, 0],
        extent: [-180, -90, 180, 90],
        projection: 'EPSG:4326',
        zoom: 2,
      }),
    });

    const svgContainer = document.createElement('div');
    const xhr = new XMLHttpRequest();
    xhr.open('GET', 'data/world.svg');
    xhr.addEventListener('load', function () {
      const svg = xhr.responseXML.documentElement;
      svgContainer.ownerDocument.importNode(svg);
      svgContainer.appendChild(svg);
    });
    xhr.send();

    const width = 2560;
    const height = 1280;
    const svgResolution = 360 / width;
    svgContainer.style.width = width + 'px';
    svgContainer.style.height = height + 'px';
    svgContainer.style.transformOrigin = 'top left';
    svgContainer.className = 'svg-layer';
    svgContainer.style.position = 'absolute';

    map.addLayer(
      new Layer({
        render: function (frameState) {
          const scale = svgResolution / frameState.viewState.resolution;
          const center = frameState.viewState.center;
          const size = frameState.size;
          const cssTransform = composeCssTransform(
            size[0] / 2,
            size[1] / 2,
            scale,
            scale,
            frameState.viewState.rotation,
            -center[0] / svgResolution - width / 2,
            center[1] / svgResolution - height / 2,
          );
          svgContainer.style.transform = cssTransform;
          svgContainer.style.opacity = String(this.getOpacity());
          return svgContainer;
        },
      }),
    );

    map.addLayer(
      new Vector({
        source: new VectorSource({
          features: [new Feature(new Point([0, 0]))],
        }),
        style: {
          'circle-fill-color': 'blue',
          'circle-radius': 10,
          'circle-stroke-color': 'white',
        },
      }),
    );

##### index.html

    <!DOCTYPE html>
    <html lang="en">
      <head>
        <meta charset="UTF-8">
        <title>SVG Layer</title>
        <link rel="stylesheet" href="node_modules/ol/ol.css">
        <style>
          .map {
            width: 100%;
            height: 400px;
          }
          #map {
            background: black;
          }

          .svg-layer path:hover {
            opacity: 0.4;
          }

          .ol-layer {
            pointer-events: none;
          }
        </style>
      </head>
      <body>
        <div id="map" class="map"></div>

        <script type="module" src="main.js"></script>
      </body>
    </html>

##### package.json

    {
      "name": "svg-layer",
      "dependencies": {
        "ol": "10.9.0"
      },
      "devDependencies": {
        "vite": "^3.2.3"
      },
      "scripts": {
        "start": "vite",
        "build": "vite build"
      }
    }