What are you folks using to host your super secret local code and why?

This obviously doesn't help for the rest of your question, but for anything that I don't want to open source for whatever reason, I just make a bare repo and push it to a folder on my server that has all my bare repos. Literally just git server on my LAN. Nothing fancy. No UI or anything, but I don't use a UI for git anyway.

If you don't have a server at home, you could do the same thing but to a folder on your local machine. That obviously means you will have no backup. But you will still have version control in case you want to revert something you did or refer back to an old version.