Please use it for at least one week, as it's a learning experience and not meant for everyone. It took me around a week to become familiar with Nix and Flakes, but I believe it was worth it since now I have to tweak things less often and my configuration's decently organized.
You could make a private repo and set up an SSH key to access it. For example, I have my dotfiles hosted on Codeberg but it's a private repo so only I have access to it (although I would not recommend putting unencrypted passwords, even in a private repository)
Although I understand if you mean not publishing to GitHub as I guess there has been some controversy and it's owned by Microsoft.