The 1st Amendment is extremely clear. The only ones calling it "ambiguous" are those looking to invent exceptions to it out of whole cloth. "What, 'no law' whatsoever? Clearly the authors and the representatives who passed this amendment couldn't have possibly objected to my reasonable proposals, so there must be some subtle nuance of interpretation at odds with the perfectly plain and unambiguous language."

If you think the definitions of religion or the press aren’t ambiguous I don’t know what to tell you, and that’s before we get into the exact meaning of the concept of “establishment”

In the context in which the text was written the meaning was perfectly obvious, since it was directed at exactly the sorts of abuses they'd just finished fighting a war over. "An establishment of religion", for example, referred to establishing an official state religion. "The freedom of speech, and of the press" was literally about speaking to each other and owning and utilizing printing presses—the use of "the press" as a general term for journalists didn't start until around 1921[0].

It's really much simpler than people make it seem.

[0] https://www.etymonline.com/word/press