This is the kind of response I was hoping for, thank you :)
Churches and religious organizations would be interesting! I hadn’t thought of that and it could lead to some cool discussions
The science agencies would be cool too. We have mander.xyz, but I worry about if they run out of funding or have other issues down the road. If nesting isn’t possible, they could do something like BeeHaw where they create the communities themselves, and set aside a page to direct to each of them.
I also didn’t think about the scouts and libraries, those would be cool too :)