This is 100% wrong.
The concept of free speech is NOT limited to the legal protections provided to US Citizens by the US Constitution.
Freedom of speech is a principle that supports the freedom of an individual or a community to articulate their opinions and ideas without fear of retaliation, censorship, or legal sanction. The right to
freedom of expression has been recognized as a human right in the Universal Declaration of Human Rights and international human rights law by the United Nations.
If Musk (or anyone else) complains that Apple should
legally be required to advertise on Twitter, then that would, of course, be ridiculous. I don't see any evidence of that happening.