I've found I'm able to embed views in the SPO "wiki page" but not in the "site page" template. I used the Page Viewer webpart - with the embed url in the Link box.
If you use the Embed web part on a "Site Page" in SPO - you will need your SPO tenant admin to add your Tableau server to the list of allowed sites for embedding:
Then it should work
I have the same question. My IT person added Tableau to the allowed list of iframe users but I don't see where I can use Wiki at all. I tried using both the embed feature and the Kindle Viewer but neither works. I could get "something" to work using embed but it doesn't actually view anything. Is this because it's an http and not a https?