Hi Johan,

Are you using there ContentArea?

In my current project we had simillar issue and ve've resolved it by explicit cast to block type.
Example code:

IEnumerable<ContentAreaItem> contentAreaItems = Enumerable.Empty<ContentAreaItem>(); // your content area items
foreach (var block in contentAreaItems.Select(c => c.GetContent() as IContentData))
{
	switch (block)
	{
		case BlockTypeA blockA:
			@Html.PropertyFor(m => blockA)
			break;
		case BlockTypeB blockB:
			@Html.PropertyFor(m => blockB)
			break;
		case null:
			break;
		default:
			<div>Block not handled.</div>
			break;
	}
}

We have a temporary fix that seems to work as before but not using PropertyFor but instead calling the View directly using:

@await Html.PartialAsync("SimpleBlock", Model.CurrentBlock.SimpleBlockTypeProperty)

// Or with extra view data...
@await Html.PartialAsync("SimpleBlock", Model.CurrentBlock.SimpleBlockTypeProperty, new ViewDataDictionary(ViewData) { { "cssClass", "some-class" } })

I recently ran into somewhat the same issue - I could not use Html.PropertyFor(x => x.Block) where Block is a actual block instance (rather than a content area or a content link). In my case, I had a dedicated view component for the block, so I just did as below. The error message is very misleading though.

@(await Component.InvokeAsync<SimpleBlockComponent>(new { currentContent = simpleBlock }))

Honestly, I think your solution is fine.