They'll still take down a repo and block the user if it is hosted. And self hosting something isn't free, plus quite possibly puts more legal exposure on the team.
This isn't a problem with technologies or the platform. There fundamentally needs to be a narrowing of DMCA, a presumption of innocence rather than guilt, and penalties for issuing unjustified takedowns.
Re: your edits, yes, DMCA reform is also important, and quite arguably more so. But decentralizing from GitHub would still slow takedowns down, and have other benefits.
IUUC importing this to GitLab would have taken ~½dozen clicks and saved the open issues, etc.?