MainActivity.cs

using System;
using Android.App;
using Android.OS;
using Android.Runtime;
using Android.Support.Design.Widget;
using Android.Support.V7.App;
using Android.Views;
using Android.Widget;

// <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

[assembly: UsesPermission(global::Android.Manifest.Permission.AccessFineLocation)]
namespace MapboxSimple
{
    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme.NoActionBar", MainLauncher = true)]
    public class MainActivity : AppCompatActivity, Codes.Redth.Ioninterop.IMapWrapperCallback
    {
        Codes.Redth.Ioninterop.MapWrapper mapWrapper;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);


            mapWrapper = new Codes.Redth.Ioninterop.MapWrapper(this, this);

            mapWrapper.Init("pk.eyJ1IjoicmVkdGgiLCJhIjoiNTQ1NjJiM2YxMjE1MmRkNTU3YmUyOTE5NjM2YzMzZDgifQ.QWjXXdDJw7eTToGFIdZh4g");


            Xamarin.Essentials.Platform.Init(this, savedInstanceState);

            SetContentView(Resource.Layout.activity_main);

            mapWrapper.OnCreate(savedInstanceState, Resource.Id.mapView);

        }

        protected override void OnResume()
        {
            base.OnResume();
            mapWrapper.OnResume();
        }

        protected override void OnStart()
        {
            base.OnStart();
            mapWrapper.OnStart();
        }

        protected override void OnPause()
        {
            base.OnPause();
            mapWrapper.OnPause();
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }

        public void MapReady()
        {
            mapWrapper.AddMarker(42.051620, -82.599159, "Redth", "Redth Lives Here (ish)");
            Console.WriteLine("Map ready!");


        }

        public void MarkerClicked(string title)
        {
            Toast.MakeText(this, title, ToastLength.Short).Show();
        }
    }
}

MapWrapper.java

package codes.redth.ioninterop;

import android.app.Activity;
import android.os.Bundle;

import androidx.annotation.NonNull;

import com.mapbox.mapboxsdk.Mapbox;
import com.mapbox.mapboxsdk.annotations.Marker;
import com.mapbox.mapboxsdk.annotations.MarkerOptions;
import com.mapbox.mapboxsdk.geometry.LatLng;
import com.mapbox.mapboxsdk.maps.MapView;
import com.mapbox.mapboxsdk.maps.MapboxMap;
import com.mapbox.mapboxsdk.maps.MapboxMapOptions;
import com.mapbox.mapboxsdk.maps.OnMapReadyCallback;
import com.mapbox.mapboxsdk.maps.Style;

public class MapWrapper {
    private final Activity parentActivity;
    private final MapWrapperCallback callbackListener;

    private MapView mapView;
    private MapboxMap map;

    public MapWrapper(Activity activity, MapWrapperCallback listener)
    {
        parentActivity = activity;
        callbackListener = listener;
    }

    public void init(String mapboxAccessToken)
    {
        Mapbox.getInstance(parentActivity, mapboxAccessToken);
    }

    public void onCreate(Bundle savedInstanceState, int mapViewResourceId)
    {
        mapView = (MapView)parentActivity.findViewById(mapViewResourceId);

        mapView.onCreate(savedInstanceState);
        mapView.getMapAsync(new OnMapReadyCallback() {
            @Override
            public void onMapReady(@NonNull MapboxMap mapboxMap) {

                map = mapboxMap;
                mapboxMap.setStyle(Style.DARK, new Style.OnStyleLoaded() {
                    @Override
                    public void onStyleLoaded(@NonNull Style style) {
                        callbackListener.mapReady();
                    }
                });
                mapboxMap.setOnMarkerClickListener(new MapboxMap.OnMarkerClickListener() {
                    @Override
                    public boolean onMarkerClick(@NonNull Marker marker) {
                        callbackListener.markerClicked(marker.getTitle());
                        return true;
                    }
                });
            }
        });
    }

    public void addMarker(double lat, double lng, String title, String snippet)
    {
        map.addMarker(new MarkerOptions()
        .position(new LatLng(lat, lng))
        .title(title)
        .setSnippet(snippet));
    }

    public void onStart()
    {
        mapView.onStart();
    }

    public void onResume()
    {
        mapView.onResume();
    }

    public void onPause()
    {
        mapView.onPause();
    }

    public void onStop()
    {
        mapView.onStop();
    }

    public void onLowMemory()
    {
        mapView.onLowMemory();
    }

    public void onDestory()
    {
        mapView.onDestroy();
    }
}

MapWrapperCallback.java

package codes.redth.ioninterop;

import com.mapbox.mapboxsdk.maps.MapboxMap;

public interface MapWrapperCallback {

    void mapReady();

    void markerClicked(String title);
}