That’s basically the question. When the Bill of Rights was being considered, did anyone advocate for Freedom of Religion as long as the practitioner was Christian? And also, at the time (c. 1789), were there any non-Christians in the US who weren’t enslaved people? I image being an atheist or a Buddhist or whatever in the late 18th century was probably not something openly discussed.
There were plenty of Jewish people and some Muslims (though almost all enslaved Muslims were forced to convert).
The first country to recognize America was Morocco and Washington explicitly called out the fact that American freedom of religion included Islam, not just Christian sects.
Deism was popular with intellectuals, including at least a few founding fathers. Though maybe heavily influenced by Christianity. I’m not expert on religious beliefs but Deism seems kinda agnostic to me.
I think it’s more like “I think some being created the universe, but it does not take interest in or notice of human activities.”
Here’s one definition from a dictionary:
”A religious belief holding that God created the universe and established rationally comprehensible moral and natural laws but does not intervene in human affairs through miracles or supernatural revelation.”
Though critically Deists had no problem turning up at church and worshiping as if they believed in a interventionist triune god (in fact thought it was a good thing for society if everyone did so) even if behind closed doors with their intellectual friends they would express deist beliefs.
To try to answer the question, Politifact (PolitiFact | Fundamentalist: When founders said ‘religion,’ they meant Christianity) says that Thomas Jefferson was a strong believer that Freedom Of Religion applied to Christians only, and even nominated a Supreme Court judge that believed the same, Joseph Story, who wrote ““The real object of the amendment was, not to countenance, much less to advance Mahometanism, or Judaism, or infidelity, by prostrating Christianity, but to exclude all rivalry among Christian sects.”
He also wrote to a Rhode Island synagogue that freedom of religion extended to Jews:
It is now no more that toleration is spoken of, as if it was by the indulgence of one class of people, that another enjoyed the exercise of their inherent natural rights. For happily the Government of the United States, which gives to bigotry no sanction, to persecution no assistance requires only that they who live under its protection should demean themselves as good citizens, in giving it on all occasions their effectual support.
The Bill of Rights was started in Congress on September 25, 1789, and finally approved by the states two years later on December 15, 1791.
Between those two dates, on Aug18, 1790, George Washington made his famous speech about religious freedom. Speaking to a Jewish audience at the synagogue in Rhode Island, he used the now-famous phrase that the new country “gives to bigotry no sanction, to persecution no assistance”.
So if we go by the public expression by the new president of the new country, it seems to me that he very much intended to include non-Christians as protected by religious freedom, even before the Bill of Rights became law.
(oops…I see that I got ninja’d by 4 minutes 
Do Deists believe in the capital “G” God of an Abrahamic deity? Or the lowercase “g” god supernatural god or gods type deities of the rest of the religions?
The examples given above seem to indicate that at the very least Abrahamic religions were included by at least by some founding fathers. Not all founding fathers were Deist though.
Please try to remember that all these cites for the opinion that Freedom of Religion means all religions doesn’t answer the question asked in the OP: Did any of the Founding Fathers have an opposing opinion that it meant freedom for Christians only?
I believe so, at least the enlightenment thinkers and founding fathers who were deists did. I think they would consider themselves Christians, even if their pastors would not (if they had explained their views to them in detail, which they did not generally do. They just turned up to church and sing hymns and made polite small talk)
At least George Washington an Thomas Jefferson seem to be think Freedom of Religion goes beyond Christianity
If Deists believe that some god created the universe but then never interfered, I don’t see how they could be traditional Christians. That doesn’t mean that deists would not find it socially useful to attend churches, though.
Madison helped Thomas Paine get out of France after the publication of “The Age of Reason.” Paine was a deist, but if you’ve read that book you will see that he was definitely not a Christian.
Thomas Jefferson was a deist, believing in what is sometimes called the “clockwork god”–a god who somehow created the world, set it up to run like a clock*, and then left it alone to run without any more interaction
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In the Declaration of Independence, Jefferson says the the people of America have reached a new status " to which the Laws of Nature and of Nature’s God entitle them". He doesn’t say the laws of God–he says the laws of Nature, and the god who belongs to Nature.
Not the God who interferes in world affairs, speaks to men and sends them to heaven or hell..
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*remember, in the 1700’s, a clock with all its precise gears, was the most complicated mechanism ever invented in human history, so it made a great image for the power of God.
But they do answer the question, “did they understand that the amendment they passed applied to non-Christians”. Clearly, they did. They didn’t just assume they were granting freedom to a variety of Christian sects.
I’d ask the related question of how many of the founding fathers objected to that right?
Here’s an interesting video about Jefferson and his view on Jesus and Christianity, particularly the trinity. Note that he describes Jesus with many descriptors, but significantly does not use anything construed as ‘Divine.’
