I’ve tried this myself and while it works in your post if I try to embed in my blog I get the error:
Firefox Can’t Open This Page
To protect your security, itch.io will not allow Firefox to display the page if another site has embedded it. To see this page, you need to open it in a new window.
I don’t know if this is intentional or an oversight. Normal embeds work fine. The HTTP response has the header “x-frame-options SAMEORIGIN” which I think causes this.