Hi Data Officer
I had this question too and found your post.
I thought of a solution - you can create an Experience using ArcGIS experience builder. Start with a fullpage blank template and add an embed widget. Make it full screen and specify the URL.
You can add experiences to the gallery on your hub page and clicking them opens the experience and therefore the page within it. Takes about half a second longer to load but my geocortex app works as intended.
Drawback or advantage depending on your stance is that the browser url shows as the experience URL and not the page URL you are intending to show.