People could just submit issues by e-mail, tbh.
I have most of my projects on either notabug or chiselapp (Fosil, not Git) and to this day I get e-mails asking for stuff or notifying about issues, so it’s not like the “social” / “Hub” aspect of “GitHub” is needed.
So, what I’m reading is, if your “users” are bad (or bots), just get better users.
Sounds like a net win.