> I have to make a full blown website just to ensure I don't get SEO-spammed into oblivion?
No, I said a crappy one on purpose. How good is it doesn't matter, the sooner the Google knows about the domain, the better. Might as well be a copy of your README file using one of the million SSGs GitHub supports that will turn that README file into a website. The only thing that matters is that the website exists and that Google knows about it before the other one.
That's why many people purchase the domain on day 1 before they even start building the thing and also why many have like a dozen domains in their account that is like a boulevard of broken dreams there to remind them once a year they haven't done anything with them.
Still cheaper than a SEO agency or in most cases even one month of ahrefs access.