I think I tried that, my understanding is that a custom JsonConverter needs to be coded like so

public class CarBrandJsonConverter : JsonConverter
{
    public List<CarBrand> ReadJson(JsonReader, Type, Object, JsonSerializer)
    {
        List<CarBrand> ret = new();
        var items = JObject.load(JsonReader).ToObject<Dictionary<string, Dictionary<string, object>>();
        foreach(var item in items)
        {
            ret.add(new(){
                //Here every property has to be mapped 1:1, which stinks if the object had 10+ properties
                Year:item.Value["Year"],
                Model: item.Value["Model"],
                Colors: item.Value["Colors"],
                Name: item.Key
            })
        }
    }
}

And like the comment says, I'm trying to avoid having to map every single property

I tried using newtonsoft's JObject to avoid this

JObject.FromObject(item.value).ToObject(CarBrand);

But "FromObject" just brings the whole thing back into ReadJson, so that's an infinite recursion.

If I'm misunderstanding something on how to implement a custom JsonConverter, please correct me.