How do I instantiate entities from a regular MonoBehaviour in ECS?

I'm loading data from an external source [call it an array of vector3 locations for the sake of this question]. I want to use it to spawn multiple instances of an entity with a renderer and some other components attached.

I have the components and systems already and I can create a GameObject in the editor (with appropriate authoring components), attach it to the subscene and get it picked up by ECS.

The problem is... I don't actually want the one in the editor, I want several thousand at locations that vary over time.

My understanding is that in an ideal, clean world, I'd create an archetype that encapsulates all the components auto-converted from the GameObject, instantiate lots of entities and set their component values as needed.

archetype = entityManager.CreateArchetype(
    typeof(RenderMesh),
    typeof(LocalToWorld),
    typeof(RenderBounds),
    typeof(ResourceProducer),  // Mine
    typeof(ResourceStockpile), // Mine
    typeof(PerInstanceCullingTag), // Added after seeing them in the inspector
    typeof(WorldToLocal_Tag),      // on the "real" entity created from the
    typeof(BlendProbeTag),         // GameObject.
    typeof(Simulate)               // May not be required.
);

I can instantiate that archetype and set the location/mesh/material but I see nothing rendered.

NativeArray<Entity> output = new NativeArray<Entity>(count, Allocator.Temp, NativeArrayOptions.UninitializedMemory);
entityManager.CreateEntity(archetype, output);

for (int i = 0; i < count; i++) {
    Entity entity = output[i];
    localToWorld[i] = new LocalToWorld {
        Value = float4x4.TRS(
                        positions[i],
                        quaternion.LookRotationSafe(math.forward(), math.up()),
                        new float3(1f, 1f, 1f))
    };

    entityManager.SetSharedComponentManaged(entity, new RenderMesh {
        mesh = mesh,
        material = material,
    });

    entityManager.SetComponentData<ResourceProducer>(entity, new ResourceProducer {
        Metal = Mathf.Max(0, UnityEngine.Random.Range(-50, 10)),
        Polymer = Mathf.Max(0, UnityEngine.Random.Range(-50, 10)),
        Ceramic = Mathf.Max(0, UnityEngine.Random.Range(-50, 10)),
        Food = (i == 0 ? 150 : 0),
        Water = Mathf.Max(0, UnityEngine.Random.Range(-50, 10)),
    });
}

[Which shows me an archetype with matching components and the right entity count in the archetypes inspector]

Conversely, I'm willing to have a prefab if it's unavoidable, but how do I mark a specific GameObject as an archetype to reference elsewhere? Does it have to be attached to the subscene? If so, how do I suppress the template object/entity?

Bakers appear to get access to a GetEntity method which I haven't seen implemented/exposed elsewhere.

I'd expose a field of type Entity and try dragging a GameObject there, but the Entity type isn't supported in the editor.

[Tangentially, is there any way I can see the raw table of entity Ids and data for a particular component? Especially entities not converted from GOs. Then I could at least validate component values are being set correctly]