That seems some what arbitrary. It is certainly not ‘only semantically’ as that is often how Buddhism is introduced in entry level Religious studies. You are using a ‘true Scotsman’ definition of Atheism. I have heard many people describe themselves as non-religious theists; they have little respect for dogma, clerical authority or religious traditions, but they still believe in a god. I would also like to know what god you think Buddhists worship.
Confucianism is also a religion that does not have a god as a central component.
Buddhism is certainly an example of a religion without a deity (or at least, without regard for a deity), but I think the OP is looking for a general term, something that would be a description of Buddhism, but which would also be a description of other religions without gods as well.
I think the term the OP is looking for is “religion.” Some - most - have a god or gods, and some don’t. That’s the general term.
The term “religion” doesn’t mean “religion that lacks a deity”.
Hmmm. That’s not what I keep seeing religious people being told when they try to insist that Atheism is a religion or requires faith - in that scenario atheism is usually characterised as not an organised or monolithic thing at all - merely comprising absence of belief in deities and not much else besides (OK, sometimes it’s non-belief in anything generally supernatural).
f you are looking for a practicing group rather than just a word or phrase, yes, go shopping among the many UUs.
One could argue that it is normal for the godhead of a given religion to tend to be minimally relevant to the teachings. “Og said this” or “doing that makes Og happy” or “masturbation makes Og kill kittens”, but for the most part, the deit(ies) are like scenery, loitering in the wings and maybe whispering to the man with the diamond ring. Jehovallah had to show up in human form to try to shed his irrelevance, but even Jesus is hardly more than background noise.