A SwitchingLinkManager for Sitecore 8.2 allowing you to use a different LinkProvider per site

ServicesConfigurationRegistration.config

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:set="http://www.sitecore.net/xmlconfig/set/">
  <sitecore>

    <services>
      <configurator type="Sitecore.Custom.Providers.ServicesConfigurator, Sitecore.Custom" />
    </services>

  </sitecore>
</configuration>

ServicesConfigurator.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Sitecore.Abstractions;
using Sitecore.DependencyInjection;

namespace Sitecore.Custom.Providers
{
    public class ServicesConfigurator : IServicesConfigurator
    {
        public void Configure(IServiceCollection serviceCollection)
        {
            var service = new ServiceDescriptor(typeof(BaseLinkManager), typeof(SwitchingLinkManager), ServiceLifetime.Singleton);
            serviceCollection.Replace(service);
        }
    }
}

SwitchingLinkManager.cs

using System;
using System.Web;
using Sitecore.Abstractions;
using Sitecore.Configuration;
using Sitecore.Data.Items;
using Sitecore.Diagnostics;
using Sitecore.Links;
using Sitecore.Sites;
using Sitecore.Web;

namespace Sitecore.Custom.Providers
{
    public class SwitchingLinkManager : BaseLinkManager
    {
        private readonly ProviderHelper<LinkProvider, LinkProviderCollection> providerHelper;

        public SwitchingLinkManager(ProviderHelper<LinkProvider, LinkProviderCollection> providerHelper)
        {
            this.providerHelper = providerHelper;
        }

        protected virtual LinkProvider Provider
        {
            get
            {
                var siteLinkProvider = (Sitecore.Context.Site != null)
                    ? Sitecore.Context.Site.Properties["linkProvider"] : String.Empty;

                if (String.IsNullOrEmpty(siteLinkProvider))
                    return this.providerHelper.Provider;

                return this.providerHelper.Providers[siteLinkProvider]
                       ?? this.providerHelper.Provider;
            }
        }

        /* below is copy/paste from Sitecore.Links.DefaultLinkManager cos Provider is marked internal :'( */

        public override bool AddAspxExtension => this.Provider.AddAspxExtension;
        public override bool AlwaysIncludeServerUrl => this.Provider.AlwaysIncludeServerUrl;
        public override LanguageEmbedding LanguageEmbedding => this.Provider.LanguageEmbedding;
        public override LanguageLocation LanguageLocation => this.Provider.LanguageLocation;
        public override bool LowercaseUrls => this.Provider.LowercaseUrls;
        public override bool ShortenUrls => this.Provider.ShortenUrls;
        public override bool UseDisplayName => this.Provider.UseDisplayName;

        public override string ExpandDynamicLinks(string text)
        {
            Assert.ArgumentNotNull(text, nameof(text));
            return this.ExpandDynamicLinks(text, false);
        }

        public override string ExpandDynamicLinks(string text, bool resolveSites)
        {
            Assert.ArgumentNotNull(text, nameof(text));
            return Assert.ResultNotNull<string>(this.Provider.ExpandDynamicLinks(text, resolveSites));
        }

        public override UrlOptions GetDefaultUrlOptions()
        {
            return Assert.ResultNotNull<UrlOptions>(this.Provider.GetDefaultUrlOptions());
        }

        public override string GetDynamicUrl(Item item)
        {
            return this.GetDynamicUrl(item, LinkUrlOptions.Empty);
        }

        public override string GetDynamicUrl(Item item, LinkUrlOptions options)
        {
            return this.Provider.GetDynamicUrl(item, options);
        }

        public override string GetItemUrl(Item item)
        {
            return this.Provider.GetItemUrl(item, this.GetDefaultUrlOptions());
        }

        public override string GetItemUrl(Item item, UrlOptions options)
        {
            return this.Provider.GetItemUrl(item, options);
        }

        public override bool IsDynamicLink(string linkText)
        {
            return this.Provider.IsDynamicLink(linkText);
        }

        public override DynamicLink ParseDynamicLink(string linkText)
        {
            return this.Provider.ParseDynamicLink(linkText);
        }

        public override RequestUrl ParseRequestUrl(HttpRequest request)
        {
            return this.Provider.ParseRequestUrl(request);
        }

        public override SiteInfo ResolveTargetSite(Item item)
        {
            Assert.ArgumentNotNull(item, nameof(item));
            return this.Provider.ResolveTargetSite(item);
        }

        public override SiteContext GetPreviewSiteContext(Item item)
        {
            Assert.ArgumentNotNull(item, nameof(item));
            return this.Provider.GetPreviewSiteContext(item);
        }
    }
}

SwitchingProvider.Sample.config

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:set="http://www.sitecore.net/xmlconfig/set/">
  <sitecore>

    <linkManager defaultProvider="default-provider">
      <providers>
        <add name="custom-provider" type="Sitecore.Links.LinkProvider, Sitecore.Kernel" 
             addAspxExtension="true" 
             alwaysIncludeServerUrl="true" 
             encodeNames="true" 
             languageEmbedding="never" 
             languageLocation="filePath" 
             lowercaseUrls="true"   
             shortenUrls="true" 
             useDisplayName="false"/>

        <add name="alternate-provider" type="MySite.Custom.Links.AlternateProvider, MySite.Custom" ... />
        <add name="default-provider" type="MySite.Custom.Links.DefaultProvider, MySite.Custom" ... />
      </providers>
    </linkManager>

    <sites>
      <site name="website"
            set:linkProvider="custom-provider" />

      <site name="my-custom-site"
            inherits="website"
            linkProvider="alternate-provider" />
    </sites>

  </sitecore>
</configuration>