Follow Twitters iFrame tree.
Which means you have to look at a Tweet and use network inspector to follow the iFrame stack to see what iFrames Twitter is using (today.
The method is outlined in the OP of The great big "I'm using WIX/SomeWebsiteMaking Tool and I don't know how to fix my embed" thread
Basically without a Tweet to look at I can’t see the iFrame stack to see what iFrames are in use