You can geocode features within a feature layer using the Esri Leaflet Geocoder plugin. You can control how general or how strict you want the search to be by specifying the search mode.
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Set different search modes</title>
    <meta name="viewport" content="initial-scale=1, maximum-scale=1, user-scalable=no">
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css" crossorigin="">
    <script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js" crossorigin=""></script>
    <!-- Load Esri Leaflet from CDN -->
    <script src="https://unpkg.com/esri-leaflet@3.0.19/dist/esri-leaflet.js"></script>
    <!-- Load Esri Leaflet Geocoder from CDN -->
    <link rel="stylesheet" href="https://unpkg.com/esri-leaflet-geocoder@3.1.6/dist/esri-leaflet-geocoder.css" crossorigin="">
    <script src="https://unpkg.com/esri-leaflet-geocoder@3.1.6/dist/esri-leaflet-geocoder.js" crossorigin=""></script>
    <!-- Load Esri Leaflet Vector from CDN -->
    <script src="https://unpkg.com/esri-leaflet-vector@4.3.2/dist/esri-leaflet-vector.js" crossorigin=""></script>
    <style>
      html,
      body,
      #map {
        padding: 0;
        margin: 0;
        height: 100%;
        width: 100%;
        font-family: Arial, Helvetica, sans-serif;
        font-size: 14px;
        color: #323232;
      }
    </style>
  </head>
  <body>
    <style>
      #selectContainer {
        position: absolute;
        top: 10px;
        right: 10px;
        z-index: 1000;
        background: white;
        padding: 1em;
      }
      #selectContainer select {
        font-size: 16px;
      }
    </style>
    <div id="map"></div>
    <div id="selectContainer" class="leaflet-bar">
      <label>
        Search Mode:
        <select id="searchMode">
          <option value="contain">contain</option>
          <option value="startWith">startWith</option>
          <option value="endWith">endWith</option>
          <option value="strict">strict</option>
        </select>
      </label>
    </div>
    <script>
      const accessToken = "YOUR_ACCESS_TOKEN";
      const map = L.map("map").setView([40.91, -96.63], 4);
      L.esri.Vector.vectorBasemapLayer("arcgis/navigation", {
        token: accessToken
      }).addTo(map);
      // searchMode can be 'contain', 'startWith', 'endWith', or 'strict'
      const gisDayProvider = L.esri.Geocoding.featureLayerProvider({
        url:
          "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/GIS_DAY_Registration/FeatureServer/0",
        searchFields: ["event_name"],
        label: "GIS Day Events 2019",
        formatSuggestion: function (feature) {
          return feature.properties.event_name;
        },
        searchMode: "contain"
      });
      L.esri.Geocoding.geosearch({
        providers: [gisDayProvider]
      }).addTo(map);
      const searchMode = document.getElementById("searchMode");
      searchMode.addEventListener("change", function () {
        gisDayProvider.options.searchMode = searchMode.value;
      });
    </script>
  </body>
</html>