I've done all the static site generators, I just don't post enough to justify the maintenance, if you do they're probably a better solution! As is, it's pretty basic but I want to add features that GitHub pages don't support
No, GitHub pages are tied to "an" account. It can be a secondary "anonymous" account. You can create an anonymous bear blog or one of the other million free writing and zero maintenance tools. It's certainly more anonymous than having to disclose your real identity via a credit card on a random person's page.
Also, what sort of content do you hope that your target audience (Bob the landscaper who is non technical but has a super urgent desire to send a message to the world in an anonymous way) will publish?