So far as I know there are no formal locations where enthusiastic non- astronomers can post their ideas about cosmology on the Internet. In several previous questions: Q738, Q403, and in other questions about the Big Bang, I have fielded inquiries about new ideas in cosmology offered by the public. My attitude has been that cosmology is a frightfully complex subject in physical science that no one should venture into without a solid background in physics and astronomy. Even I as an astronomer do not do much more than review and learn about the ideas of physicists and cosmologists when it comes to trying to understand this subject. I do not presuppose that I am competent to create a new cosmological theory as an astronomer, that would be any kind of significant improvement over Big Bang cosmology.
I think the equivalent area in other professions would be a site where you could publish alternate methods for wiring a house or installing its plumbing. No matter what the novel ideas might be, they still have to pass a building code inspection when you are done. Alternate ways of interpreting US law would also be an interesting intellectual exercise, but again, the final test is what the Judge and the Supreme Court have to say about your idea. Modern science works the same way, not by vote of some authority, but by compliance of the new idea with observational evidence and the large body of observations and laws that have been established previously.
If the goal of such a discussion area is simply to come to a personal understanding of where modern cosmology is, then that's fine. If, however, you harbor a hope that any of your efforts will advance modern cosmology in a formal way, then the chances of a non-physicist doing this are worse than winning a state lottery. It is, however, a compelling intellectual exercise to try to resolve the many intuitive paradoxes in relativistic Big Bang cosmology. If you can find a better way to moditivate what expanding space is all about, then God bless you! The famous 'balloon analogy' has worn pretty thin over the decades!!