Alright, let's dig into the counterexamples.

Ethical Culture, or Ethical Humanism, doesn't call itself a religion but recognizes it fills some roles parallel to religious practice. The Ethical movement started as an explicitly secular idea and has grown/split/changed over a couple hundred years. Some branches call themselves religions, some even embrace spirituality (and not just in the way Felix Adler tried to redefine it as a kind of moral drive.) Already we're in a space where we have to accept that words mean multiple things depending on context, and I'm being flippant because it seemed obvious that in this conversation it isn't useful to use the term "religion" to mean multiple things when alternatives exist. It's not "contested" there are several valid definitions but that can't be applied interchangeably. Language should facilitate the communication of ideas, not muddy it. Furthering that point is the concept of a secular religion. This started as a critique of Christianity or "any religion, for that matter" and through that it should be assumed that subsequent use of the word "religion" in the thread was the type or types that could be applied to Christianity.

Regardless, we carry on.

Humanistic Judaism is essentially the same thing as Ethical Humanism but retaining the cultural heritage and rituals of Judaism (or part of it, they aren't a monolith). They make a distinction between "religious and secular traditions" implying that secularity is explicitly nonreligious in their point of view.

Unitarian Universalists do call themselves a religion and they are not a secular movement. The belief in a "higher power" of some kind is important to their identity and they don't shy away from language like "faith" or "religious practice." It's a rejection of dogma or enforcing specific creeds and will accept pretty much anyone because they're more interested in inclusiveness than spirituality but it's a beige religion attached to cuddly social justice movement.

So yeah, I stand by what I said. For the purposes of this conversation the difference between a religion and a philosophy is magic.