Sorry, but tl;dr? The link you posted is deep into some drama I don't know what it's referring to.

TL;DR; .NET Foundation moved all member projects to be a suborg of .NET Foundation without asking maintainers.

For example, I am a maintainer of https://github.com/pythonnet/. If you follow that link, you will see "Part of .NET Foundation" which is a GitHub Enterprise Organization.

AFAIU, They could do that because when joining projects needed to add dnfadmin@github bot, that was supposed to perform some utility tasks such as enforcing CLAs.

I don't see "Part of .NET Foundation" anywhere on that page.

It is right under the project name next to the logo.

I also don't see it. Possibly it only shows for people logged in with an account that is associated in some way?

You are right. It does not show in private browser mode.

Allegedly some actions required .net foundation to have admin access to projects under their umbrella. The foundation then changed the copyright notices to dotnetfoundation instead of the actual owners.

I didn't understand the drama above the comments entirely, though.

I don't see any copyright notices being changed in the PR in question: https://github.com/reactiveui/splat/pull/778/files

Legally, copyright notices can only be changed by the copyright holder or their authorized agent. If someone from the DNF were to make an unauthorized, illegal change, it would be very surprising.