Twitter is transforming into X, as the site’s former bird logo has now been replaced by an official new X logo. Elon Musk, who owns the transformed social media site, began signaling the change early Sunday morning with a series of tweets, starting with one that said, “and soon we shall bid adieu to the twitter brand and, gradually, all the birds.”
It’s the X from AGFA Monotype Special Alphabets 4.
https://catalog.monotype.com/font/monotype/special-alphabets/4