Yeah, that was my point in the first comment... But not only that...
The development with multiple people is decentralized, yes...
But even, if I add 3 remotes to my repo (1 to GitHub, 1 to Forgejo instance A and 1 to Forgejo instance B), guess what happens, if you don't have an account on each of these... Try pushing code or making a pull request and see how it fails, because you are not authenticated...