In the latest release of PineBlog I've added support for .Net Core 3.0 (and 3.1-preview3) and removed support for .Net Core 2.2. There are no mayor changes in the package. But since .Net Core 3.x has some changes in the Startup.cs, you might need to update the registration of PineBlog there.

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.AddPineBlog(Configuration); 

    // when you want to add just the bare minimum
    services.AddRazorPages().AddPineBlogRazorPages();

    // or you can use the more familiar ways from .Net Core 2.x
    // or services.AddMvcCore().AddPineBlogRazorPages();
    // or services.AddMvc().AddPineBlogRazorPages();
    ...
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    ...
    app.UseEndpoints(endpoints =>
    {
        // make sure to add the endpoint mapping for both RazorPages and Controllers
        endpoints.MapRazorPages();
        endpoints.MapControllers();
    });
    ...
}

For more information, please check PineBlog on GitHub.