You can use other forges, but they have the exact same issues as GitHub. You need to make an account, you need to accept terms of service and if they feel like it (or are forced by a court) they’ll ban you and your repository.
git send-email exists. So it’s not like you absolutely can’t contribute to projects that are hosted on GitHub.
At some point in the future gitlab will get federation, but that’s not a solution for now. It’ll take a while.