I have 4.0.0-beta-7 installed. I am currently investigating how best to use itemscope and its properties on my sites, so I had a look at Cassiopeia to see how it's used there.

What needs to be fixed

I discovered that if you have a menu item with an article or blog in the <main> section, the first <div> looks something like this with a browser's inspector:

<div class="com-content-article item-page" itemscope="" itemtype="https://schema.org/Article">

Why this should be fixed

It should be itemscope without the ="", i.e.
<div class="com-content-article item-page" itemscope itemtype="https://schema.org/Article">

It's the same in J3.9x

See https://schema.org/docs/gs.html showing how it should be used.

How would you fix it

In this file [4.0-dev] joomla-cms/components/com_content/tmpl/article/default.php it is correct, so I don't know when or how the extra ="" is being added or how to fix it.

Side Effects expected

None