I need to just derive stuff from something, and all the derived types I'll register somewhere, or initialize, or something like that - but I don't want to also have to have an ever-growing list of tasks for each

var subtypes = AppDomain.CurrentDomain.GetAssemblies()
    .SelectMany(domainAssembly => domainAssembly.GetTypes())
    .Where(type => type.IsSubclassOf(typeof(MyAbstractClass)) && !type.IsAbstract)
    .ToList();
 
foreach (var subtype in subtypes)
{
    var instance = (MyAbstractClass) Activator.CreateInstance(subtype);
}

so you make an abstract class `MyAbstractClass` and derive from it.

static List<Task<Report>> CollectReporters(Configuration conf)
{
    var toReturn = new List<Task<Report>>();
 
    var reporterTypes = AppDomain.CurrentDomain.GetAssemblies()
      .SelectMany(domainAssembly => domainAssembly.GetTypes())
      .Where(type => type.IsSubclassOf(typeof(newsletter.Reporters.Reporter)) && !type.IsAbstract)
      .ToList();
    var skipPortionInName = "newsletter.Reporters.".Length;
 
 
    foreach(var discoveredConfType in conf.Reporters.Select(r => r.ReporterClass))
    {
        Console.WriteLine($"{discoveredConfType} configuration type discovered");
    }
    foreach (var reporterType in reporterTypes)
    {
        Console.WriteLine($"{reporterType.ToString().Substring(skipPortionInName).ToLower()} reporter class discovered");
        Func<Configuration.Reporter, bool> predicate = r => r.ReporterClass == reporterType.ToString().Substring(skipPortionInName).ToLower();
        if (!conf.Reporters.Any(predicate))
        {
            Console.WriteLine($"no configurations for it");
        }
        else
        {
            var configurationsFor = conf.Reporters.Where(predicate);
            Console.WriteLine($"{configurationsFor.Count()} configurations for it");
 
            foreach (var confFor in configurationsFor)
            {
                 var instance = (newsletter.Reporters.Reporter) Activator.CreateInstance(reporterType);
                toReturn.Add(instance.Report(confFor));
            }
        }
    }
 
    return toReturn;
}

observe - I write a text string in a config file to describ ea type, and now I can pick what object to instantiate :)))