It's trivial if your project is trivial. Once you've got development/CI/CD workflows, releases, issue management, community interaction, maybe even project management or Github pages (may god have mercy on your soul), it gets a lot less trivial.

Git itself is a distributed version control system, moving it around is indeed trivial. It's everything else that Github provides that is far less trivial, and they've worked hard on building the vendor lock-in elements for those things lately.

A big issue though is that you can't move other people's projects for them. If I want to contribute to Immich, I have to be on GitHub. Cloning it somewhere the maintainers aren't looking or accepting contributions does nothing.