I’m finding a lot of literature from NGOs specializing in US jurisprudence saying the first amendment has been interpreted to protect public, obvious recording[1].

If I tried to draw up an indentured servitude contract, what federal or state laws would explicitly forbid enforcing it myself? If state laws, do all states have equivalent laws?

[1]: https://www.freedomforum.org/recording-in-public/

The First Amendment protects you against prosecution for filming the actions of law enforcement in a public venue. AFAIK it hasn’t been interpreted to void state laws that might forbid someone from recording a conversation between private individuals who don’t consent. The link you provided says as much.

How do you self-enforce an indentured servitude contract? Or any contract, for that matter? Only a court can compel performance or restitution for a breach of contract.