It is not about leading anything but about having the code in a repository so that it is easy to read/consult/audit/etc.
You can upload the code to any service (it doesn't have to be GitHub, it can be GitLab, sourcehut, etc...) and disable issues and comments.
I recommend Matrix with the Conduit server. This server requires almost no resources and even runs on a Raspberry Pi.
Cinny works perfectly as a desktop client (in case you want to escape from the ubiquitous Element). And for mobile I would use Element for Android/iOS although FluffyChat also works very well.