How are we responding to beliefs other than a Christianity?

I'm certain they are free to post religious materials, perhaps you could ask them why they do not. At 1% of the populations, there should be about 4,900 Native American Rally Point members.

They’re free to post it, I’m not going to do it for them though...

Of course my religion is vaguely defined as “I like trees” so what do I know?

As a family with Oneida Tribe connections I think the reasons are tied to the fact that traditional Native American ceremonial ways can vary widely and are based on the differing histories, practices, theology and beliefs of individual tribes, clans, and bands. Traditional beliefs are usually passed down in the forms of oral histories, stories, allegories, and principles, and rely on face to face teaching in one's family and community, they are not normally written down.