@Bierbasstard Yes, I've heard that individual congregations (their preferred term, they don't like the label "church" ) vary in their practical openness to non-theists, and that an individual congregation can evolve over time in that regard, too. I'm not clear how autonomous each congregation is from the mothership, but I gather they get a pretty free reign. This actually isn't unheard of even in Christianity; the churches I grew up in belonged to the IFCA (Independent Fundamental Churches of America) and were entirely self-governed. The IFCA simply provided a common doctrinal statement, similar to a creed, to which all subscribed, so that you knew the ideology you were sitting under, and provided some shared services like "pulpit supply" (list of approved speakers who would fill in for a missing or ill pastor and perhaps offer themselves for a permanent position).

There are also regional differences in UU congregations, for example, a UU order of service in the Bible Belt will look far more evangelical in overall form than one up here in the NorthEast, even while almost comically including hymnody from non-Christian traditions.

Then there's the example of a woman we know in our area who's a retired Episcopal priest with, shall we say, very strong personal Views, which she offers up in her sermons in various area churches where she's invited to speak, pretty much in opposition to the local bishop's stated policies. If he fires her she doesn't really give a fig at this point in her life.

This kind of thing is why it's important to understand the governing structure of any church you might get involved with, to the extent you want to be comfortable in the stability of various policies and practices that might be deal-breakers for you. Sometimes if you find a church you can live with, the reasons you can live with it may be quite fragile and changeable.

@Sealybobo
It always pays to stay on your toes.